Fix single keyframe animations. (#14344)

# Objective

For clips with more than one curve, only the first was being applied if
there is only one keyframe in it.

## Solution

Continue!

crates/bevy_animation/src/lib.rs

@@ -875,12 +875,12 @@ impl AnimationTargetContext<'_> {
             // Some curves have only one keyframe used to set a transform
             if curve.keyframe_timestamps.len() == 1 {
                 self.apply_single_keyframe(curve, weight);
-                return;
+                continue;
             }
 
             // Find the current keyframe
             let Some(step_start) = curve.find_current_keyframe(seek_time) else {
-                return;
+                continue;
             };
 
             let timestamp_start = curve.keyframe_timestamps[step_start];