### 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
_create_children_cache();
	int visible_count = 0;
	for (int i = 0; i < children_cache.size(); i++) {
		if (children_cache[i]->is_visible()) {
			visible_count += 1;
		}
	}
	return visible_count;
}
int TreeItem::get_child_count() {
	_create_children_cache();
	return children_cache.size();
}
TypedArray<TreeItem> TreeItem::get_children() {
	
	int size = get_child_count();
	TypedArray<TreeItem> arr;
	arr.resize(size);
	for (int i = 0; i < size; i++) {
		arr[i] = children_cache[i];
	}
	return arr;
}
int TreeItem::get_index() {