### 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)

EditorInspectorArray *editor_inspector_array = nullptr;
			StringName array_element_prefix;
			Color c = sscolor;
			c.a /= level;
			Vector<String> class_name_components = String(p.class_name).split(",");
			int page_size = 5;
			bool movable = true;
			bool numbered = false;
			bool foldable = use_folding;
			String add_button_text = TTR("Add Element");
			String swap_method;
			for (int i = (p.type == Variant::NIL ? 1 : 2); i < class_name_components.size(); i++) {
				if (class_name_components[i].begins_with("page_size") && class_name_components[i].get_slice_count("=") == 2) {
					page_size = class_name_components[i].get_slice("=", 1).to_int();
				} else if (class_name_components[i].begins_with("add_button_text") && class_name_components[i].get_slice_count("=") == 2) {
					add_button_text = class_name_components[i].get_slice("=", 1).strip_edges();
				} else if (class_name_components[i] == "static") {
					movable = false;
				} else if (class_name_components[i] == "numbered") {
					numbered = true;
				} else if (class_name_components[i] == "unfoldable") {
					foldable = false;
				} else if (class_name_components[i].begins_with("swap_method") && class_name_components[i].get_slice_count("=") == 2) {
					swap_method = class_name_components[i].get_slice("=", 1).strip_edges();
				}
			}
			if (p.type == Variant::NIL) {
				
				array_element_prefix = class_name_components[0];
				editor_inspector_array = memnew(EditorInspectorArray(all_read_only));