### 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)

subgroup = p.name;
			Vector<String> hint_parts = p.hint_string.split(",");
			subgroup_base = hint_parts[0];
			if (hint_parts.size() > 1) {
				section_depth = hint_parts[1].to_int();
			} else {
				section_depth = 0;
			}
			continue;
		} else if (p.usage & PROPERTY_USAGE_GROUP) {
			
			group = p.name;
			Vector<String> hint_parts = p.hint_string.split(",");
			group_base = hint_parts[0];
			if (hint_parts.size() > 1) {
				section_depth = hint_parts[1].to_int();
			} else {
				section_depth = 0;
			}
			subgroup = "";
			subgroup_base = "";
			continue;
		} else if (p.usage & PROPERTY_USAGE_CATEGORY) {
			
			group = "";
			group_base = "";
			subgroup = "";
			subgroup_base = "";
			section_depth = 0;
			if (!show_categories) {