Merge pull request #71139 from TokageItLab/fix-anim-length-edit-undo

Fix undo of editing animation length with spinner by adding flag

editor/animation_track_editor.cpp

@@ -1253,7 +1253,7 @@ void AnimationTimelineEdit::_anim_length_changed(double p_new_len) {
 
 	editing = true;
 	Ref<EditorUndoRedoManager> &undo_redo = EditorNode::get_undo_redo();
-	undo_redo->create_action(TTR("Change Animation Length"));
+	undo_redo->create_action(TTR("Change Animation Length"), UndoRedo::MERGE_ENDS);
 	undo_redo->add_do_method(animation.ptr(), "set_length", p_new_len);
 	undo_redo->add_undo_method(animation.ptr(), "set_length", animation->get_length());
 	undo_redo->commit_action();