### 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)

label = p_label;
	queue_redraw();
}
String EditorProperty::get_label() const {
	return label;
}
Object *EditorProperty::get_edited_object() {
	return object;
}
StringName EditorProperty::get_edited_property() const {
	return property;
}
void EditorProperty::set_doc_path(const String &p_doc_path) {
	doc_path = p_doc_path;
}
void EditorProperty::update_property() {
	GDVIRTUAL_CALL(_update_property);
}
void EditorProperty::_set_read_only(bool p_read_only) {
}
void EditorProperty::set_read_only(bool p_read_only) {
	read_only = p_read_only;
	if (GDVIRTUAL_CALL(_set_read_only, p_read_only)) {
		return;
	}
	_set_read_only(p_read_only);
}
bool EditorProperty::is_read_only() const {