### 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)

undo_redo->add_undo_method(object, swap_method, i, i - 1);
					}
				}
			}
		} else {
			
			List<PropertyInfo> object_property_list;
			object->get_property_list(&object_property_list);
			Array properties_as_array = _extract_properties_as_array(object_property_list);
			properties_as_array.resize(count);
			
			undo_redo->add_undo_property(object, count_property, properties_as_array.size());
			for (int i = 0; i < (int)properties_as_array.size(); i++) {
				Dictionary d = Dictionary(properties_as_array[i]);
				Array keys = d.keys();
				for (int j = 0; j < keys.size(); j++) {
					String key = keys[j];
					undo_redo->add_undo_property(object, vformat(key, i), d[key]);
				}
			}
			if (p_element_index < 0) {
				
				properties_as_array.insert(p_to_pos < 0 ? properties_as_array.size() : p_to_pos, Dictionary());
			} else if (p_to_pos < 0) {
				
				properties_as_array.remove_at(p_element_index);
			} else {
				
				properties_as_array.insert(p_to_pos, properties_as_array[p_element_index].duplicate());
				properties_as_array.remove_at(p_to_pos < p_element_index ? p_element_index + 1 : p_element_index);