### 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)

}
			
			if (dropping && !vbox->is_visible_in_tree()) {
				Color accent_color = get_theme_color(SNAME("accent_color"), SNAME("Editor"));
				draw_rect(Rect2(Point2(), get_size()), accent_color, false);
			}
			
			if (section_indent_style.is_valid() && section_indent > 0) {
				Rect2 indent_rect = Rect2(Vector2(), Vector2(indent_depth * section_indent_size, get_size().height));
				if (rtl) {
					indent_rect.position.x = get_size().width - section_indent + section_indent_style->get_margin(SIDE_RIGHT);
				} else {
					indent_rect.position.x = section_indent_style->get_margin(SIDE_LEFT);
				}
				draw_style_box(section_indent_style, indent_rect);
			}
		} break;
		case NOTIFICATION_DRAG_BEGIN: {
			dropping_for_unfold = true;
		} break;
		case NOTIFICATION_DRAG_END: {
			dropping_for_unfold = false;
		} break;
		case NOTIFICATION_MOUSE_ENTER: {
			if (dropping || dropping_for_unfold) {
				dropping_unfold_timer->start();
			}
			queue_redraw();
		} break;
		case NOTIFICATION_MOUSE_EXIT: {