If a mesh without any vertex attributes is rendered (for example, one that only has indices), bevy will crash since the mesh still creates a vertex buffer even though it's empty. Later code assumes that there is vertex data, causing an index-out-of-bounds panic. This PR fixes the issue by adding a check that there is any vertex data before creating a vertex buffer.
I ran into this issue while rendering a tilemap without any vertex attributes (only indices).
Stack trace:
```
thread 'main' panicked at 'index out of bounds: the len is 0 but the index is 0', C:\Dev\Games\bevy\crates\bevy_render\src\render_graph\nodes\pass_node.rs:346:9
stack backtrace:
0: std::panicking::begin_panic_handler
at /rustc/bb491ed23937aef876622e4beb68ae95938b3bf9\/library\std\src\panicking.rs:493
1: core::panicking::panic_fmt
at /rustc/bb491ed23937aef876622e4beb68ae95938b3bf9\/library\core\src\panicking.rs:92
2: core::panicking::panic_bounds_check
at /rustc/bb491ed23937aef876622e4beb68ae95938b3bf9\/library\core\src\panicking.rs:69
3: core::slice::index::{{impl}}::index<core::option::Option<tuple<bevy_render::renderer::render_resource::buffer::BufferId, u64>>>
at C:\Users\tehpe\.rustup\toolchains\nightly-x86_64-pc-windows-msvc\lib\rustlib\src\rust\library\core\src\slice\index.rs:184
4: core::slice::index::{{impl}}::index<core::option::Option<tuple<bevy_render::renderer::render_resource::buffer::BufferId, u64>>,usize>
at C:\Users\tehpe\.rustup\toolchains\nightly-x86_64-pc-windows-msvc\lib\rustlib\src\rust\library\core\src\slice\index.rs:15
5: alloc::vec::{{impl}}::index<core::option::Option<tuple<bevy_render::renderer::render_resource::buffer::BufferId, u64>>,usize,alloc::alloc::Global>
at C:\Users\tehpe\.rustup\toolchains\nightly-x86_64-pc-windows-msvc\lib\rustlib\src\rust\library\alloc\src\vec\mod.rs:2386
6: bevy_render::render_graph::nodes::pass_node::DrawState::is_vertex_buffer_set
at C:\Dev\Games\bevy\crates\bevy_render\src\render_graph\nodes\pass_node.rs:346
7: bevy_render::render_graph::nodes::pass_node::{{impl}}::update::{{closure}}<bevy_render::render_graph::base::MainPass*>
at C:\Dev\Games\bevy\crates\bevy_render\src\render_graph\nodes\pass_node.rs:285
8: bevy_wgpu::renderer::wgpu_render_context::{{impl}}::begin_pass
at C:\Dev\Games\bevy\crates\bevy_wgpu\src\renderer\wgpu_render_context.rs:196
9: bevy_render::render_graph::nodes::pass_node::{{impl}}::update<bevy_render::render_graph::base::MainPass*>
at C:\Dev\Games\bevy\crates\bevy_render\src\render_graph\nodes\pass_node.rs:244
10: bevy_wgpu::renderer::wgpu_render_graph_executor::WgpuRenderGraphExecutor::execute
at C:\Dev\Games\bevy\crates\bevy_wgpu\src\renderer\wgpu_render_graph_executor.rs:75
11: bevy_wgpu::wgpu_renderer::{{impl}}::run_graph::{{closure}}
at C:\Dev\Games\bevy\crates\bevy_wgpu\src\wgpu_renderer.rs:115
12: bevy_ecs::world::World::resource_scope<bevy_render::render_graph::graph::RenderGraph,tuple<>,closure-0>
at C:\Dev\Games\bevy\crates\bevy_ecs\src\world\mod.rs:715
13: bevy_wgpu::wgpu_renderer::WgpuRenderer::run_graph
at C:\Dev\Games\bevy\crates\bevy_wgpu\src\wgpu_renderer.rs:104
14: bevy_wgpu::wgpu_renderer::WgpuRenderer::update
at C:\Dev\Games\bevy\crates\bevy_wgpu\src\wgpu_renderer.rs:121
15: bevy_wgpu::get_wgpu_render_system::{{closure}}
at C:\Dev\Games\bevy\crates\bevy_wgpu\src\lib.rs:112
16: alloc::boxed::{{impl}}::call_mut<tuple<mut bevy_ecs::world::World*>,FnMut<tuple<mut bevy_ecs::world::World*>>,alloc::alloc::Global>
at C:\Users\tehpe\.rustup\toolchains\nightly-x86_64-pc-windows-msvc\lib\rustlib\src\rust\library\alloc\src\boxed.rs:1553
17: bevy_ecs::system::exclusive_system::{{impl}}::run
at C:\Dev\Games\bevy\crates\bevy_ecs\src\system\exclusive_system.rs:41
18: bevy_ecs::schedule::stage::{{impl}}::run
at C:\Dev\Games\bevy\crates\bevy_ecs\src\schedule\stage.rs:812
19: bevy_ecs::schedule::Schedule::run_once
at C:\Dev\Games\bevy\crates\bevy_ecs\src\schedule\mod.rs:201
20: bevy_ecs::schedule::{{impl}}::run
at C:\Dev\Games\bevy\crates\bevy_ecs\src\schedule\mod.rs:219
21: bevy_app::app::App::update
at C:\Dev\Games\bevy\crates\bevy_app\src\app.rs:58
22: bevy_winit::winit_runner_with::{{closure}}
at C:\Dev\Games\bevy\crates\bevy_winit\src\lib.rs:485
23: winit::platform_impl::platform::event_loop::{{impl}}::run_return::{{closure}}<tuple<>,closure-1>
at C:\Users\tehpe\.cargo\registry\src\github.com-1ecc6299db9ec823\winit-0.24.0\src\platform_impl\windows\event_loop.rs:203
24: alloc::boxed::{{impl}}::call_mut<tuple<winit::event::Event<tuple<>>, mut winit::event_loop::ControlFlow*>,FnMut<tuple<winit::event::Event<tuple<>>, mut winit::event_loop::ControlFlow*>>,alloc::alloc::Global>
at C:\Users\tehpe\.rustup\toolchains\nightly-x86_64-pc-windows-msvc\lib\rustlib\src\rust\library\alloc\src\boxed.rs:1553
25: winit::platform_impl::platform::event_loop:🏃:{{impl}}::call_event_handler::{{closure}}<tuple<>>
at C:\Users\tehpe\.cargo\registry\src\github.com-1ecc6299db9ec823\winit-0.24.0\src\platform_impl\windows\event_loop\runner.rs:245
26: std::panic::{{impl}}::call_once<tuple<>,closure-0>
at C:\Users\tehpe\.rustup\toolchains\nightly-x86_64-pc-windows-msvc\lib\rustlib\src\rust\library\std\src\panic.rs:344
27: std::panicking::try::do_call<std::panic::AssertUnwindSafe<closure-0>,tuple<>>
at C:\Users\tehpe\.rustup\toolchains\nightly-x86_64-pc-windows-msvc\lib\rustlib\src\rust\library\std\src\panicking.rs:379
28: hashbrown::set::HashSet<mut winapi::shared::windef::HWND__*, std::collections:#️⃣:map::RandomState, alloc::alloc::Global>::iter<mut winapi::shared::windef::HWND__*,std::collections:#️⃣:map::RandomState,alloc::alloc::Global>
29: std::panicking::try<tuple<>,std::panic::AssertUnwindSafe<closure-0>>
at C:\Users\tehpe\.rustup\toolchains\nightly-x86_64-pc-windows-msvc\lib\rustlib\src\rust\library\std\src\panicking.rs:343
30: std::panic::catch_unwind<std::panic::AssertUnwindSafe<closure-0>,tuple<>>
at C:\Users\tehpe\.rustup\toolchains\nightly-x86_64-pc-windows-msvc\lib\rustlib\src\rust\library\std\src\panic.rs:431
31: winit::platform_impl::platform::event_loop:🏃:EventLoopRunner<tuple<>>::catch_unwind<tuple<>,tuple<>,closure-0>
at C:\Users\tehpe\.cargo\registry\src\github.com-1ecc6299db9ec823\winit-0.24.0\src\platform_impl\windows\event_loop\runner.rs:152
32: winit::platform_impl::platform::event_loop:🏃:EventLoopRunner<tuple<>>::call_event_handler<tuple<>>
at C:\Users\tehpe\.cargo\registry\src\github.com-1ecc6299db9ec823\winit-0.24.0\src\platform_impl\windows\event_loop\runner.rs:239
33: winit::platform_impl::platform::event_loop:🏃:EventLoopRunner<tuple<>>::move_state_to<tuple<>>
at C:\Users\tehpe\.cargo\registry\src\github.com-1ecc6299db9ec823\winit-0.24.0\src\platform_impl\windows\event_loop\runner.rs:341
34: winit::platform_impl::platform::event_loop:🏃:EventLoopRunner<tuple<>>::main_events_cleared<tuple<>>
at C:\Users\tehpe\.cargo\registry\src\github.com-1ecc6299db9ec823\winit-0.24.0\src\platform_impl\windows\event_loop\runner.rs:227
35: winit::platform_impl::platform::event_loop::flush_paint_messages<tuple<>>
at C:\Users\tehpe\.cargo\registry\src\github.com-1ecc6299db9ec823\winit-0.24.0\src\platform_impl\windows\event_loop.rs:676
36: winit::platform_impl::platform::event_loop::thread_event_target_callback::{{closure}}<tuple<>>
at C:\Users\tehpe\.cargo\registry\src\github.com-1ecc6299db9ec823\winit-0.24.0\src\platform_impl\windows\event_loop.rs:1967
37: std::panic::{{impl}}::call_once<isize,closure-0>
at C:\Users\tehpe\.rustup\toolchains\nightly-x86_64-pc-windows-msvc\lib\rustlib\src\rust\library\std\src\panic.rs:344
38: std::panicking::try::do_call<std::panic::AssertUnwindSafe<closure-0>,isize>
at C:\Users\tehpe\.rustup\toolchains\nightly-x86_64-pc-windows-msvc\lib\rustlib\src\rust\library\std\src\panicking.rs:379
39: hashbrown::set::HashSet<mut winapi::shared::windef::HWND__*, std::collections:#️⃣:map::RandomState, alloc::alloc::Global>::iter<mut winapi::shared::windef::HWND__*,std::collections:#️⃣:map::RandomState,alloc::alloc::Global>
40: std::panicking::try<isize,std::panic::AssertUnwindSafe<closure-0>>
at C:\Users\tehpe\.rustup\toolchains\nightly-x86_64-pc-windows-msvc\lib\rustlib\src\rust\library\std\src\panicking.rs:343
41: std::panic::catch_unwind<std::panic::AssertUnwindSafe<closure-0>,isize>
at C:\Users\tehpe\.rustup\toolchains\nightly-x86_64-pc-windows-msvc\lib\rustlib\src\rust\library\std\src\panic.rs:431
42: winit::platform_impl::platform::event_loop:🏃:EventLoopRunner<tuple<>>::catch_unwind<tuple<>,isize,closure-0>
at C:\Users\tehpe\.cargo\registry\src\github.com-1ecc6299db9ec823\winit-0.24.0\src\platform_impl\windows\event_loop\runner.rs:152
43: winit::platform_impl::platform::event_loop::thread_event_target_callback<tuple<>>
at C:\Users\tehpe\.cargo\registry\src\github.com-1ecc6299db9ec823\winit-0.24.0\src\platform_impl\windows\event_loop.rs:2151
44: DefSubclassProc
45: DefSubclassProc
46: CallWindowProcW
47: DispatchMessageW
48: SendMessageTimeoutW
49: KiUserCallbackDispatcher
50: NtUserDispatchMessage
51: DispatchMessageW
52: winit::platform_impl::platform::event_loop::EventLoop<tuple<>>::run_return<tuple<>,closure-1>
at C:\Users\tehpe\.cargo\registry\src\github.com-1ecc6299db9ec823\winit-0.24.0\src\platform_impl\windows\event_loop.rs:218
53: winit::platform_impl::platform::event_loop::EventLoop<tuple<>>::run<tuple<>,closure-1>
at C:\Users\tehpe\.cargo\registry\src\github.com-1ecc6299db9ec823\winit-0.24.0\src\platform_impl\windows\event_loop.rs:188
54: winit::event_loop::EventLoop<tuple<>>::run<tuple<>,closure-1>
at C:\Users\tehpe\.cargo\registry\src\github.com-1ecc6299db9ec823\winit-0.24.0\src\event_loop.rs:154
55: bevy_winit::run<closure-1>
at C:\Dev\Games\bevy\crates\bevy_winit\src\lib.rs:171
56: bevy_winit::winit_runner_with
at C:\Dev\Games\bevy\crates\bevy_winit\src\lib.rs:493
57: bevy_winit::winit_runner
at C:\Dev\Games\bevy\crates\bevy_winit\src\lib.rs:211
58: core::ops::function::Fn::call<fn(bevy_app::app::App),tuple<bevy_app::app::App>>
at C:\Users\tehpe\.rustup\toolchains\nightly-x86_64-pc-windows-msvc\lib\rustlib\src\rust\library\core\src\ops\function.rs:70
59: alloc::boxed::{{impl}}::call<tuple<bevy_app::app::App>,Fn<tuple<bevy_app::app::App>>,alloc::alloc::Global>
at C:\Users\tehpe\.rustup\toolchains\nightly-x86_64-pc-windows-msvc\lib\rustlib\src\rust\library\alloc\src\boxed.rs:1560
60: bevy_app::app::App::run
at C:\Dev\Games\bevy\crates\bevy_app\src\app.rs:68
61: bevy_app::app_builder::AppBuilder::run
at C:\Dev\Games\bevy\crates\bevy_app\src\app_builder.rs:54
62: game_main::main
at .\crates\game_main\src\main.rs:23
63: core::ops::function::FnOnce::call_once<fn(),tuple<>>
at C:\Users\tehpe\.rustup\toolchains\nightly-x86_64-pc-windows-msvc\lib\rustlib\src\rust\library\core\src\ops\function.rs:227
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.
Apr 27 21:51:01.026 ERROR gpu_descriptor::allocator: `DescriptorAllocator` is dropped while some descriptor sets were not deallocated
error: process didn't exit successfully: `target/cargo\debug\game_main.exe` (exit code: 0xc000041d)
```
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