Fix gdnative config file set as null
Fix gdnative config file set as null

Fixes #45997.

Setting a GDNativeLibrary config file as null or any other object but a ConfigFile will now cause an error.

(cherry picked from commit 618dd892f59be0f1d527da29b8cd904ad67bc915)

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