### 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
ERR_FAIL_INDEX(p_column, cells.size());
	cells.write[p_column].selectable = p_selectable;
}
bool TreeItem::is_selectable(int p_column) const {
	ERR_FAIL_INDEX_V(p_column, cells.size(), false);
	return cells[p_column].selectable;
}
bool TreeItem::is_selected(int p_column) {
	ERR_FAIL_INDEX_V(p_column, cells.size(), false);
	return cells[p_column].selectable && cells[p_column].selected;
}
void TreeItem::set_as_cursor(int p_column) {
	ERR_FAIL_INDEX(p_column, cells.size());
	if (!tree) {
		return;
	}
	if (tree->select_mode != Tree::SELECT_MULTI) {
		return;
	}
	if (tree->selected_item == this && tree->selected_col == p_column) {
		return;
	}
	tree->selected_item = this;
	tree->selected_col = p_column;
	tree->queue_redraw();
}
void TreeItem::select(int p_column) {