### Godot version

4.0 beta 10

### System information

Windows 11 Vulkan

### Issue description

Looked through the issues list, but couldn't find something like this, sorry in advance if this has already been reported.

There is a few cases (in the pictures below) where list of Actions in Input Map may not always show a scrollbar even if the actions list overflows (I imagine this could also happen for the widget that Input Map uses).

![image](https://user-images.githubusercontent.com/39958198/210003566-cf60dbaf-921f-485b-b0a9-51ffc28d0244.png)

![New Bitmap image](https://user-images.githubusercontent.com/39958198/210004079-8eb2e6a1-0cf5-4a7c-8905-a4e3cfd0ec5d.png)

![image](https://user-images.githubusercontent.com/39958198/210004165-a6b6790b-248a-4f68-b4d0-b44b25afdf4f.png)

![image](https://user-images.githubusercontent.com/39958198/210004537-aca52194-a464-48b9-b818-24782706de45.png)


### Steps to reproduce

The pictures are clearer than anything I could write here: "a picture is worth 1000 words"

### Minimal reproduction project

N/A
parent->children_cache.insert(0, this);
		}
	}
	prev = item_prev;
	next = p_item;
	p_item->prev = this;
	if (tree && old_tree == tree) {
		tree->queue_redraw();
	}
	validate_cache();
}
void TreeItem::move_after(TreeItem *p_item) {
	ERR_FAIL_NULL(p_item);
	ERR_FAIL_COND(is_root);
	ERR_FAIL_COND(!p_item->parent);
	if (p_item == this) {
		return;
	}
	TreeItem *p = p_item->parent;
	while (p) {
		ERR_FAIL_COND_MSG(p == this, "Can't move to a descendant");
		p = p->parent;
	}
	Tree *old_tree = tree;
	_unlink_from_tree();
	_change_tree(p_item->tree);
	if (p_item->next) {
		p_item->next->prev = this;
	}
	parent = p_item->parent;