### Godot version

4.0.dev (c309de53997feff3286295fb2d71657f112a15db)

### System information

Linux, Nvidia, Vulkan

### Issue description

Editor segfaults when certain conditions are met when using the AnimationPlayer editor.

### Steps to reproduce

1. Create multiple animations, saved into a animation collection
2. Open an existing animation, then make a new empty animation
3. Change from seconds to fps, or add a new property to animate ()
4. Editor crashes

NOTE: It is slightly random and I have not found a perfect repro

### Minimal reproduction project

N/A (TBD?)
StringName anim_name = p_value;
						if (!setting) {
							setting = true;
							undo_redo->create_action(TTR("Animation Multi Change Keyframe Value"), UndoRedo::MERGE_ENDS);
						}
						StringName prev = animation->animation_track_get_key_animation(track, key);
						undo_redo->add_do_method(animation.ptr(), "animation_track_set_key_animation", track, key, anim_name);
						undo_redo->add_undo_method(animation.ptr(), "animation_track_set_key_animation", track, key, prev);
						update_obj = true;
					}
				} break;
			}
		}
	}
	EditorUndoRedoManager *undo_redo = EditorUndoRedoManager::get_singleton();
	if (setting) {
		if (update_obj) {
			undo_redo->add_do_method(this, "_update_obj", animation);
			undo_redo->add_undo_method(this, "_update_obj", animation);
		}
		undo_redo->commit_action();
		setting = false;
		if (change_notify_deserved) {
			notify_change();
		}
		return true;
	}
	return false;
}
bool AnimationMultiTrackKeyEdit::_get(const StringName &p_name, Variant &r_ret) const {