### 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
if (!is_inside_tree()) {
		defer_load_scene = p_scene;
		return OK;
	}
	if (!p_set_inherited) {
		for (int i = 0; i < editor_data.get_edited_scene_count(); i++) {
			if (editor_data.get_scene_path(i) == p_scene) {
				_scene_tab_changed(i);
				return OK;
			}
		}
		if (!p_force_open_imported && FileAccess::exists(p_scene + ".import")) {
			open_imported->set_text(vformat(TTR("Scene '%s' was automatically imported, so it can't be modified.\nTo make changes to it, a new inherited scene can be created."), p_scene.get_file()));
			open_imported->popup_centered();
			new_inherited_button->grab_focus();
			open_import_request = p_scene;
			return OK;
		}