### 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
#include "scene/gui/dialogs.h"
#include "scene/gui/file_dialog.h"
#include "scene/gui/link_button.h"
#include "scene/gui/menu_bar.h"
#include "scene/gui/menu_button.h"
#include "scene/gui/panel.h"
#include "scene/gui/panel_container.h"
#include "scene/gui/popup.h"
#include "scene/gui/rich_text_label.h"
#include "scene/gui/split_container.h"
#include "scene/gui/tab_bar.h"
#include "scene/gui/tab_container.h"
#include "scene/main/window.h"
#include "scene/property_utils.h"
#include "scene/resources/packed_scene.h"
#include "servers/display_server.h"
#include "servers/navigation_server_3d.h"
#include "servers/physics_server_2d.h"
#include "editor/audio_stream_preview.h"
#include "editor/debugger/editor_debugger_node.h"
#include "editor/debugger/script_editor_debugger.h"
#include "editor/dependency_editor.h"
#include "editor/editor_about.h"
#include "editor/editor_audio_buses.h"
#include "editor/editor_build_profile.h"
#include "editor/editor_command_palette.h"
#include "editor/editor_data.h"
#include "editor/editor_feature_profile.h"
#include "editor/editor_folding.h"
#include "editor/editor_help.h"