### Godot version

v4.0.beta17.mono.official [c40020513]

### System information

Window 11, Forward+, GTX 1060

### Issue description

Adding two theme variations in a row result to a  crash.

https://user-images.githubusercontent.com/93253123/217037249-1ce1d56d-beb6-4435-83ad-9f8a07fe0e96.mp4



### Steps to reproduce

1. Create a project.
2. Create a theme.
3. Double click to go in the theme editor.
4. Click on manage items buttons.
5. In the add type field type a name to add a type.
6. type another name to add a second type.
7. Crash.

### Minimal reproduction project

[ThemeVariationCrash.zip](https://github.com/godotengine/godot/files/10665863/ThemeVariationCrash.zip)

return InspectorDock::get_singleton() && InspectorDock::get_inspector_singleton() == this;
}
void EditorInspector::_property_changed(const String &p_path, const Variant &p_value, const String &p_name, bool p_changing, bool p_update_all) {
	
	
	if (p_changing) {
		this->changing++;
	}
	_edit_set(p_path, p_value, p_update_all, p_name);
	if (p_changing) {
		this->changing--;
	}
	if (restart_request_props.has(p_path)) {
		emit_signal(SNAME("restart_requested"));
	}
}
void EditorInspector::_multiple_properties_changed(Vector<String> p_paths, Array p_values, bool p_changing) {