### 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)

}
	}
}
static Control *make_help_bit(const String &p_text, bool p_property) {
	EditorHelpBit *help_bit = memnew(EditorHelpBit);
	help_bit->get_rich_text()->set_custom_minimum_size(Size2(360 * EDSCALE, 1));
	PackedStringArray slices = p_text.split("::", false);
	if (slices.is_empty()) {
		
		help_bit->set_text(p_text);
		return help_bit;
	}
	String property_name = slices[0].strip_edges();
	String text;
	if (p_property) {
		text = TTR("Property:") + " ";
	}
	text += "[u][b]" + property_name + "[/b][/u]";
	if (slices.size() > 1) {
		String property_doc = slices[1].strip_edges();
		if (property_name != property_doc) {
			text += "\n" + property_doc;
		}
	} else {
		text += "\n[i]" + TTR("No description.") + "[/i]";
	}
	help_bit->set_text(text);
	return help_bit;
}
Control *EditorProperty::make_custom_tooltip(const String &p_text) const {