### 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 < plugins_list.size(); i++) {
		plugins_list[i]->make_visible(p_visible);
	}
}
void EditorPluginList::edit(Object *p_object) {
	for (int i = 0; i < plugins_list.size(); i++) {
		plugins_list[i]->edit(p_object);
	}
}
bool EditorPluginList::forward_gui_input(const Ref<InputEvent> &p_event) {
	bool discard = false;
	for (int i = 0; i < plugins_list.size(); i++) {
		if (plugins_list[i]->forward_canvas_gui_input(p_event)) {
			discard = true;
		}
	}
	return discard;
}
EditorPlugin::AfterGUIInput EditorPluginList::forward_3d_gui_input(Camera3D *p_camera, const Ref<InputEvent> &p_event, bool serve_when_force_input_enabled) {