reorderClips method
Implementation
void reorderClips(int oldIndex, int newIndex) {
if (oldIndex < 0 || oldIndex >= _clips.length) return;
if (newIndex > oldIndex) newIndex--;
if (newIndex < 0 || newIndex >= _clips.length) return;
final clip = _clips.removeAt(oldIndex);
_clips.insert(newIndex, clip);
_selectedClipIndex = newIndex;
}