### 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)

for (const StringName &F : filtered_names) {
				TreeItem *item_node = import_items_tree->create_item(data_type_node);
				item_node->set_meta("_can_be_imported", true);
				item_node->set_text(0, F);
				item_node->set_cell_mode(IMPORT_ITEM, TreeItem::CELL_MODE_CHECK);
				item_node->set_checked(IMPORT_ITEM, false);
				item_node->set_editable(IMPORT_ITEM, true);
				item_node->set_cell_mode(IMPORT_ITEM_DATA, TreeItem::CELL_MODE_CHECK);
				item_node->set_checked(IMPORT_ITEM_DATA, false);
				item_node->set_editable(IMPORT_ITEM_DATA, true);
				_restore_selected_item(item_node);
				item_node->propagate_check(IMPORT_ITEM, false);
				item_node->propagate_check(IMPORT_ITEM_DATA, false);
				item_list->push_back(item_node);
			}
		}
		
		if (!is_matching_filter && !has_filtered_items) {
			root->remove_child(type_node);
			memdelete(type_node);
			continue;
		}
		
		if (!filter_text.is_empty() && has_filtered_items) {
			type_node->set_collapsed(false);
		}
	}
	if (color_amount > 0) {
		Array arr;
		arr.push_back(color_amount);