instance-scene: make parent as edited_scene if no parent selected.
instance-scene: make parent as edited_scene if no parent selected.

(cherry picked from commit 9eb3546f38621b068c736d335d8926897b486175)

ex/godot,ex/godot,ex/godot,ex/godot,ex/godot,ex/godot,ex/godot,ex/godot