Avoid any possibility of using scene from different main in CTX_data_scene_layer

While these functions might be considered a temporary solution, please still be
very accurate about data ownership and where data is coming from.

source/blender/blenkernel/intern/context.c

@@ -915,7 +915,7 @@ SceneLayer *CTX_data_scene_layer(const bContext *C)
 		return sl;
 	}
 	else {
-		return BKE_scene_layer_context_active(CTX_data_scene(C));
+		return BKE_scene_layer_context_active_ex(CTX_data_main(C), CTX_data_scene(C));
 	}
 }