### 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)

ep->set_checkable(checkable);
				ep->set_checked(checked);
				ep->set_keying(keying);
				ep->set_read_only(property_read_only || all_read_only);
				ep->set_deletable(deletable_properties || p.name.begins_with("metadata/"));
			}
			current_vbox->add_child(editors[i].property_editor);
			if (ep) {
				
				bool update_all = (p.usage & PROPERTY_USAGE_UPDATE_ALL_IF_MODIFIED);
				ep->connect("property_changed", callable_mp(this, &EditorInspector::_property_changed).bind(update_all));
				ep->connect("property_keyed", callable_mp(this, &EditorInspector::_property_keyed));
				ep->connect("property_deleted", callable_mp(this, &EditorInspector::_property_deleted), CONNECT_DEFERRED);
				ep->connect("property_keyed_with_value", callable_mp(this, &EditorInspector::_property_keyed_with_value));
				ep->connect("property_checked", callable_mp(this, &EditorInspector::_property_checked));
				ep->connect("property_pinned", callable_mp(this, &EditorInspector::_property_pinned));
				ep->connect("selected", callable_mp(this, &EditorInspector::_property_selected));
				ep->connect("multiple_properties_changed", callable_mp(this, &EditorInspector::_multiple_properties_changed));
				ep->connect("resource_selected", callable_mp(this, &EditorInspector::_resource_selected), CONNECT_DEFERRED);
				ep->connect("object_id_selected", callable_mp(this, &EditorInspector::_object_id_selected), CONNECT_DEFERRED);
				if (!doc_info.description.is_empty()) {
					ep->set_tooltip_text(property_prefix + p.name + "::" + doc_info.description);
				} else {
					ep->set_tooltip_text(property_prefix + p.name);
				}
				ep->set_doc_path(doc_info.path);
				ep->update_property();
				ep->_update_pin_flags();
				ep->update_editor_property_status();
				ep->update_cache();