### 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)

p_control->connect("focus_entered", callable_mp(this, &EditorProperty::_focusable_focused).bind(focusables.size()));
	focusables.push_back(p_control);
}
void EditorProperty::select(int p_focusable) {
	bool already_selected = selected;
	if (p_focusable >= 0) {
		ERR_FAIL_INDEX(p_focusable, focusables.size());
		focusables[p_focusable]->grab_focus();
	} else {
		selected = true;
		queue_redraw();
	}
	if (!already_selected && selected) {
		emit_signal(SNAME("selected"), property, selected_focusable);
	}
}
void EditorProperty::deselect() {
	selected = false;
	selected_focusable = -1;
	queue_redraw();
}
bool EditorProperty::is_selected() const {
	return selected;
}
void EditorProperty::gui_input(const Ref<InputEvent> &p_event) {
	ERR_FAIL_COND(p_event.is_null());
	if (property == StringName()) {
		return;
	}