### 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
ProjectSettings *ps = ProjectSettings::get_singleton();
	PackedStringArray enabled_plugins = ps->get("editor_plugins/enabled");
	for (int i = 0; i < enabled_plugins.size(); ++i) {
		if (enabled_plugins.get(i) == p_name) {
			enabled_plugins.remove_at(i);
			break;
		}
	}
	ps->set("editor_plugins/enabled", enabled_plugins);
}
void EditorNode::_plugin_over_edit(EditorPlugin *p_plugin, Object *p_object) {
	if (p_object) {
		editor_plugins_over->add_plugin(p_plugin);
		p_plugin->make_visible(true);
		p_plugin->edit(p_object);
	} else {
		editor_plugins_over->remove_plugin(p_plugin);
		p_plugin->make_visible(false);
		p_plugin->edit(nullptr);
	}
}
void EditorNode::_resources_changed(const Vector<String> &p_resources) {