### 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)

if (property == StringName()) {
		return; 
	}
	bool new_pinned = false;
	if (can_pin) {
		Node *node = Object::cast_to<Node>(object);
		CRASH_COND(!node);
		new_pinned = node->is_property_pinned(property);
	}
	Variant current = object->get(_get_revert_property());
	bool new_can_revert = EditorPropertyRevert::can_property_revert(object, property, &current) && !is_read_only();
	bool new_checked = checked;
	if (checkable) { 
		bool valid = false;
		Variant value = object->get(property, &valid);
		if (valid) {
			new_checked = value.get_type() != Variant::NIL;
		}
	}
	if (new_can_revert != can_revert || new_pinned != pinned || new_checked != checked) {
		if (new_can_revert != can_revert) {
			emit_signal(SNAME("property_can_revert_changed"), property, new_can_revert);
		}
		can_revert = new_can_revert;
		pinned = new_pinned;
		checked = new_checked;
		queue_redraw();
	}
}
bool EditorProperty::use_keying_next() const {