### 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 (update_spinner_step >= 8) {
					update_spinner_step = 0;
				}
				update_spinner_step_msec = tick;
				update_spinner_step_frame = frame + 1;
				
				if (EDITOR_GET("interface/editor/show_update_spinner")) {
					update_spinner->set_icon(gui_base->get_theme_icon("Progress" + itos(update_spinner_step + 1), SNAME("EditorIcons")));
				}
			}
			editor_selection->update();
			ResourceImporterTexture::get_singleton()->update_imports();
			if (settings_changed) {
				_update_title();
			}
			if (settings_changed) {
				_update_from_settings();
				settings_changed = false;
				emit_signal(SNAME("project_settings_changed"));
			}
			ResourceImporterTexture::get_singleton()->update_imports();
			bottom_panel_updating = false;
		} break;
		case NOTIFICATION_ENTER_TREE: {
			get_tree()->set_disable_node_threading(true); 
			Engine::get_singleton()->set_editor_hint(true);
			Window *window = get_window();
			if (window) {
				
				window->connect("titlebar_changed", callable_mp(this, &EditorNode::_titlebar_resized));