### Godot version

4.1 rc3

### System information

Windows 10.0.19045 - Vulkan (Forward+) - dedicated NVIDIA GeForce GTX 1060 (NVIDIA; 30.0.15.1403) - Intel(R) Core(TM) i7-7700HQ CPU @ 2.80GHz (8 Threads)

### Issue description

This™
![image](https://github.com/godotengine/godot/assets/2223172/cb33110f-a5b0-400a-951f-3fa425f05714)

It can still happen, but it's more difficult to trigger.

### Steps to reproduce

1. Create a new scene with a Control node
2. Add Theme to the Control
3. Open Theme Editor
4. Clear the `theme` property in Control
5. Save, with Theme Editor opened
6. Restart

### Minimal reproduction project

N/A
scene_root->set_snap_2d_transforms_to_pixel(snap_2d_transforms);
	bool snap_2d_vertices = GLOBAL_GET("rendering/2d/snap/snap_2d_vertices_to_pixel");
	scene_root->set_snap_2d_vertices_to_pixel(snap_2d_vertices);
	Viewport::SDFOversize sdf_oversize = Viewport::SDFOversize(int(GLOBAL_GET("rendering/2d/sdf/oversize")));
	scene_root->set_sdf_oversize(sdf_oversize);
	Viewport::SDFScale sdf_scale = Viewport::SDFScale(int(GLOBAL_GET("rendering/2d/sdf/scale")));
	scene_root->set_sdf_scale(sdf_scale);
	Viewport::MSAA msaa = Viewport::MSAA(int(GLOBAL_GET("rendering/anti_aliasing/quality/msaa_2d")));
	scene_root->set_msaa_2d(msaa);
	float mesh_lod_threshold = GLOBAL_GET("rendering/mesh_lod/lod_change/threshold_pixels");
	scene_root->set_mesh_lod_threshold(mesh_lod_threshold);
	RS::get_singleton()->decals_set_filter(RS::DecalFilter(int(GLOBAL_GET("rendering/textures/decals/filter"))));
	RS::get_singleton()->light_projectors_set_filter(RS::LightProjectorFilter(int(GLOBAL_GET("rendering/textures/light_projectors/filter"))));
	SceneTree *tree = get_tree();
	tree->set_debug_collisions_color(GLOBAL_GET("debug/shapes/collision/shape_color"));
	tree->set_debug_collision_contact_color(GLOBAL_GET("debug/shapes/collision/contact_color"));
#ifdef DEBUG_ENABLED
	NavigationServer3D::get_singleton()->set_debug_navigation_edge_connection_color(GLOBAL_GET("debug/shapes/navigation/edge_connection_color"));
	NavigationServer3D::get_singleton()->set_debug_navigation_geometry_edge_color(GLOBAL_GET("debug/shapes/navigation/geometry_edge_color"));
	NavigationServer3D::get_singleton()->set_debug_navigation_geometry_face_color(GLOBAL_GET("debug/shapes/navigation/geometry_face_color"));
	NavigationServer3D::get_singleton()->set_debug_navigation_geometry_edge_disabled_color(GLOBAL_GET("debug/shapes/navigation/geometry_edge_disabled_color"));
	NavigationServer3D::get_singleton()->set_debug_navigation_geometry_face_disabled_color(GLOBAL_GET("debug/shapes/navigation/geometry_face_disabled_color"));
	NavigationServer3D::get_singleton()->set_debug_navigation_enable_edge_connections(GLOBAL_GET("debug/shapes/navigation/enable_edge_connections"));
	NavigationServer3D::get_singleton()->set_debug_navigation_enable_edge_connections_xray(GLOBAL_GET("debug/shapes/navigation/enable_edge_connections_xray"));
	NavigationServer3D::get_singleton()->set_debug_navigation_enable_edge_lines(GLOBAL_GET("debug/shapes/navigation/enable_edge_lines"));
	NavigationServer3D::get_singleton()->set_debug_navigation_enable_edge_lines_xray(GLOBAL_GET("debug/shapes/navigation/enable_edge_lines_xray"));
	NavigationServer3D::get_singleton()->set_debug_navigation_enable_geometry_face_random_color(GLOBAL_GET("debug/shapes/navigation/enable_geometry_face_random_color"));
#endif 
}
void EditorNode::_select_default_main_screen_plugin() {