### Godot version

4.2 dev1

### System information

Windows 10.0.19045 - Vulkan (Forward+) - dedicated NVIDIA GeForce GTX 1060 (NVIDIA; 30.0.15.1403) - Intel(R) Core(TM) i7-7700HQ CPU @ 2.80GHz (8 Threads)

### Issue description

Calling `Tree.propagate_check()` after an item is unchecked does not properly uncheck the parents. They are left in partially checked state.

It's easy to observe in theme editor:

https://github.com/godotengine/godot/assets/2223172/71d0479c-0a5e-48d3-957f-d90379a95c22



### Steps to reproduce

1. Edit a Theme resource
2. Go to Manage Items... menu
3. Go to Import Items tab
4. Unfold something
5. Check and uncheck a child checkbox

### Minimal reproduction project

N/A
return tree;
}
TreeItem *TreeItem::get_next() const {
	return next;
}
TreeItem *TreeItem::get_prev() {
	if (prev) {
		return prev;
	}
	if (!parent || parent->first_child == this) {
		return nullptr;
	}
	
	TreeItem *l_prev = parent->first_child;
	while (l_prev && l_prev->next != this) {
		l_prev = l_prev->next;
	}
	prev = l_prev;
	return prev;
}
TreeItem *TreeItem::get_parent() const {