### 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)

select_all_font_sizes_button = memnew(Button);
	select_full_font_sizes_button = memnew(Button);
	total_selected_font_sizes_label = memnew(Label);
	select_icons_icon = memnew(TextureRect);
	select_icons_label = memnew(Label);
	deselect_all_icons_button = memnew(Button);
	select_all_icons_button = memnew(Button);
	select_full_icons_button = memnew(Button);
	total_selected_icons_label = memnew(Label);
	select_styleboxes_icon = memnew(TextureRect);
	select_styleboxes_label = memnew(Label);
	deselect_all_styleboxes_button = memnew(Button);
	select_all_styleboxes_button = memnew(Button);
	select_full_styleboxes_button = memnew(Button);
	total_selected_styleboxes_label = memnew(Label);
	for (int i = 0; i < Theme::DATA_TYPE_MAX; i++) {
		Theme::DataType dt = (Theme::DataType)i;
		TextureRect *select_items_icon = nullptr;
		Label *select_items_label = nullptr;
		Button *deselect_all_items_button = nullptr;
		Button *select_all_items_button = nullptr;
		Button *select_full_items_button = nullptr;
		Label *total_selected_items_label = nullptr;
		String items_title;
		String select_all_items_tooltip;
		String select_full_items_tooltip;
		String deselect_all_items_tooltip;
		switch (dt) {
			case Theme::DATA_TYPE_COLOR:
				select_items_icon = select_colors_icon;