### 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 (DisplayServer::get_singleton()->window_can_draw()) {
				ProjectSettings::get_singleton()->save();
			}
			_titlebar_resized();
			
		} break;
		case NOTIFICATION_APPLICATION_FOCUS_IN: {
			
			OS::get_singleton()->set_low_processor_usage_mode_sleep_usec(int(EDITOR_GET("interface/editor/low_processor_mode_sleep_usec")));
			EditorFileSystem::get_singleton()->scan_changes();
			_scan_external_changes();
		} break;
		case NOTIFICATION_APPLICATION_FOCUS_OUT: {
			
			if (EDITOR_GET("interface/editor/save_on_focus_loss")) {
				_menu_option_confirm(FILE_SAVE_SCENE, false);
			}
			
			OS::get_singleton()->set_low_processor_usage_mode_sleep_usec(int(EDITOR_GET("interface/editor/unfocused_low_processor_mode_sleep_usec")));
		} break;
		case NOTIFICATION_WM_ABOUT: {
			show_about();
		} break;
		case NOTIFICATION_WM_CLOSE_REQUEST: {
			_menu_option_confirm(FILE_QUIT, false);
		} break;
		case EditorSettings::NOTIFICATION_EDITOR_SETTINGS_CHANGED: {
			scene_tabs->set_tab_close_display_policy((TabBar::CloseButtonDisplayPolicy)EDITOR_GET("interface/scene_tabs/display_close_button").operator int());
			FileDialog::set_default_show_hidden_files(EDITOR_GET("filesystem/file_dialog/show_hidden_files"));
			EditorFileDialog::set_default_show_hidden_files(EDITOR_GET("filesystem/file_dialog/show_hidden_files"));