### 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
ERR_FAIL_NULL(p_editing_owner);
	if (p_object && _is_class_editor_disabled_by_feature_profile(p_object->get_class())) {
		return;
	}
	Vector<EditorPlugin *> item_plugins;
	if (p_object) {
		item_plugins = editor_data.get_subeditors(p_object);
	}
	if (!item_plugins.is_empty()) {
		ObjectID owner_id = p_editing_owner->get_instance_id();
		List<EditorPlugin *> to_remove;
		for (EditorPlugin *plugin : active_plugins[owner_id]) {
			if (!item_plugins.has(plugin)) {
				
				to_remove.push_back(plugin);
				_plugin_over_edit(plugin, nullptr);
			}
		}
		for (EditorPlugin *plugin : to_remove) {
			active_plugins[owner_id].erase(plugin);