### 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
pick_main_scene->set_meta("from_native", p_from_native); 
	String main_scene = GLOBAL_GET("application/run/main_scene");
	if (main_scene.is_empty()) {
		current_menu_option = -1;
		pick_main_scene->set_text(TTR("No main scene has ever been defined, select one?\nYou can change it later in \"Project Settings\" under the 'application' category."));
		pick_main_scene->popup_centered();
		if (editor_data.get_edited_scene_root()) {
			select_current_scene_button->set_disabled(false);
			select_current_scene_button->grab_focus();
		} else {
			select_current_scene_button->set_disabled(true);
		}
		return false;
	}
	if (!FileAccess::exists(main_scene)) {
		current_menu_option = -1;
		pick_main_scene->set_text(vformat(TTR("Selected scene '%s' does not exist, select a valid one?\nYou can change it later in \"Project Settings\" under the 'application' category."), main_scene));
		pick_main_scene->popup_centered();
		return false;
	}
	if (ResourceLoader::get_resource_type(main_scene) != "PackedScene") {
		current_menu_option = -1;
		pick_main_scene->set_text(vformat(TTR("Selected scene '%s' is not a scene file, select a valid one?\nYou can change it later in \"Project Settings\" under the 'application' category."), main_scene));
		pick_main_scene->popup_centered();
		return false;
	}
	return true;
}
void EditorNode::_immediate_dialog_confirmed() {