### 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)

OPTION_MOVE_UP = 0,
		OPTION_MOVE_DOWN,
		OPTION_NEW_BEFORE,
		OPTION_NEW_AFTER,
		OPTION_REMOVE,
		OPTION_CLEAR_ARRAY,
		OPTION_RESIZE_ARRAY,
	};
	int popup_array_index_pressed = -1;
	PopupMenu *rmb_popup = nullptr;
	struct ArrayElement {
		PanelContainer *panel = nullptr;
		MarginContainer *margin = nullptr;
		HBoxContainer *hbox = nullptr;
		TextureRect *move_texture_rect = nullptr;
		Label *number = nullptr;
		VBoxContainer *vbox = nullptr;
		Button *erase = nullptr;
	};
	LocalVector<ArrayElement> array_elements;
	Ref<StyleBoxFlat> odd_style;
	Ref<StyleBoxFlat> even_style;
	int _get_array_count();
	void _add_button_pressed();