### 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
if (icon.is_null()) {
		return Size2();
	}
	if (icon_region == Rect2i()) {
		return icon->get_size();
	} else {
		return icon_region.size;
	}
}
void TreeItem::Cell::draw_icon(const RID &p_where, const Point2 &p_pos, const Size2 &p_size, const Color &p_color) const {
	if (icon.is_null()) {
		return;
	}
	Size2i dsize = (p_size == Size2()) ? icon->get_size() : p_size;
	if (icon_region == Rect2i()) {
		icon->draw_rect_region(p_where, Rect2(p_pos, dsize), Rect2(Point2(), icon->get_size()), p_color);
	} else {
		icon->draw_rect_region(p_where, Rect2(p_pos, dsize), icon_region, p_color);
	}
}
void TreeItem::_changed_notify(int p_cell) {