### 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
emit_signal(SNAME("cell_selected"));
		queue_redraw();
	} else {
		int col = selected_col < 0 ? 0 : selected_col;
		while (prev && !prev->cells[col].selectable) {
			prev = prev->get_prev_visible();
		}
		if (!prev) {
			return; 
		}
		prev->select(col);
	}
	ensure_cursor_is_visible();
	accept_event();
}
void Tree::_go_down() {
	TreeItem *next = nullptr;
	if (!selected_item) {
		if (root) {
			next = hide_root ? root->get_next_visible() : root;
		}
	} else {
		next = selected_item->get_next_visible();
		if (last_keypress != 0) {
			
			int col;
			next = _search_item_text(next, incr_search, &col, true);
			if (!next) {
				accept_event();
				return;