### 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)

return make_help_bit(p_text, false);
}
Size2 EditorInspectorCategory::get_minimum_size() const {
	Ref<Font> font = get_theme_font(SNAME("bold"), SNAME("EditorFonts"));
	int font_size = get_theme_font_size(SNAME("bold_size"), SNAME("EditorFonts"));
	Size2 ms;
	ms.height = font->get_height(font_size);
	if (icon.is_valid()) {
		ms.height = MAX(icon->get_height(), ms.height);
	}
	ms.height += get_theme_constant(SNAME("v_separation"), SNAME("Tree"));
	return ms;
}
EditorInspectorCategory::EditorInspectorCategory() {
}
void EditorInspectorSection::_test_unfold() {
	if (!vbox_added) {
		add_child(vbox);
		move_child(vbox, 0);
		vbox_added = true;
	}
}
Ref<Texture2D> EditorInspectorSection::_get_arrow() {