Another night another question

Descrated temple reads:

Action: When a [Choas] unit you control leaves play, destroy target development.

Does this force the controller to destroy their own development if there are no other developments in play? I would guess no because is doesn't say "forced" but the word "when" seems like it could be confused.

It's an Action. Actions are optional so if the player with the Temple is the only player with any developments, he can simply choose not to take that Action.