Fix lighting_dirty flag bug

In rare circumstances, changing the geometry data attached to an instance, there was the opporunity for the lighting_dirty flag to get out of sync, which could lead to access to a stale light RID, and warnings or worse.

This PR fixes the problem by ensuring the lighting is always updated on the instance when first adding GeometryData.

servers/visual/visual_server_scene.h

@@ -324,7 +324,7 @@ public:
 		List<Instance *> lightmap_captures;
 
 		InstanceGeometryData() {
-			lighting_dirty = false;
+			lighting_dirty = true;
 			reflection_dirty = true;
 			can_cast_shadows = true;
 			material_is_animated = true;