### 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)

bottom_editor = p_control;
}
Variant EditorProperty::_get_cache_value(const StringName &p_prop, bool &r_valid) const {
	return object->get(p_prop, &r_valid);
}
bool EditorProperty::is_cache_valid() const {
	if (object) {
		for (const KeyValue<StringName, Variant> &E : cache) {
			bool valid;
			Variant value = _get_cache_value(E.key, valid);
			if (!valid || value != E.value) {
				return false;
			}
		}
	}
	return true;
}
void EditorProperty::update_cache() {
	cache.clear();
	if (object && property != StringName()) {
		bool valid;
		Variant value = _get_cache_value(property, valid);
		if (valid) {
			cache[property] = value;
		}
	}
}
Variant EditorProperty::get_drag_data(const Point2 &p_point) {