Crash when inserting rotation keyframe

### Tested versions

Godot Engine v4.3.stable.flathub

### System information

Godot v4.3.stable (77dcf97d8) - Freedesktop SDK 24.08 (Flatpak runtime) - X11 - Vulkan (Forward+) - dedicated AMD Radeon RX 6600 (RADV NAVI23) - 12th Gen Intel(R) Core(TM) i5-12600K (16 Threads)

### Issue description

crash occurs when attempting to insert a rotation keyframe on a bone in this hierarchy
spine -> spine.001 -> spine.002 -> spine.003 -> upper_arm.L
the skeleton and model mesh are imported from an FBX i downloaded off of itch.io
here: [https://dblob-ua.itch.io/low-poly-characterchar-ronin-01](url)

### Steps to reproduce

1. download the file and import it to godot
2. open it as a new inherited scene
3. place the animation track as a child to Skeleton3D
4. create a new animation
5. add upper_arm.L and upper_arm.R rotation to the track
6. insert a keyframe

godot will crash.

### Minimal reproduction project (MRP)

[keyframe_crash.zip](https://github.com/user-attachments/files/17605539/keyframe_crash.zip)