Transform Track can't be edited for empty actor when reopen sequencer

This is a remaining issue of [Link Removed].
It became able to edit transform track. But, transform track can't edit when reopen after once save.

1. Create a new level sequence
2. from Modes panel, drag an empty actor and drop it to sequencer
3. The actor is now added as a spawnable, and edit transform track.
4. Level sequencer save and close.
5. Reset transform and Track can't be edited when reopen sequencer.