### 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
for (int i = 0; i < editor_data.get_edited_scene_count(); i++) {
		if (editor_data.get_scene_path(i) == p_path) {
			return true;
		}
	}
	return false;
}
void EditorNode::fix_dependencies(const String &p_for_file) {
	dependency_fixer->edit(p_for_file);
}
int EditorNode::new_scene() {
	int idx = editor_data.add_edited_scene(-1);
	
	if (editor_data.get_edited_scene_count() > 1) {
		for (int i = 0; i < editor_data.get_edited_scene_count() - 1; i++) {
			bool unsaved = EditorUndoRedoManager::get_singleton()->is_history_unsaved(editor_data.get_scene_history_id(i));
			if (!unsaved && editor_data.get_scene_path(i).is_empty() && editor_data.get_edited_scene_root(i) == nullptr) {
				editor_data.remove_scene(i);
				idx--;
			}
		}
	}
	idx = MAX(idx, 0);
	_scene_tab_changed(idx);
	editor_data.clear_editor_states();
	_update_scene_tabs();
	return idx;
}
Error EditorNode::load_scene(const String &p_scene, bool p_ignore_broken_deps, bool p_set_inherited, bool p_clear_errors, bool p_force_open_imported, bool p_silent_change_tab) {