### 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
Point2 click_pos = get_global_mouse_position() - get_global_position();
				if (!get_item_at_position(click_pos)) {
					pressed_button = -1;
					cache.click_type = Cache::CLICK_NONE;
					return -1;
				}
				pressed_button = j;
				cache.click_type = Cache::CLICK_BUTTON;
				cache.click_index = j;
				cache.click_id = c.buttons[j].id;
				cache.click_item = p_item;
				cache.click_column = col;
				cache.click_pos = click_pos;
				queue_redraw();
				return -1;
			}
			col_width -= w + theme_cache.button_margin;
		}
		if (p_button == MouseButton::LEFT || (p_button == MouseButton::RIGHT && allow_rmb_select)) {
			
			if (p_double_click && (!c.editable || c.mode == TreeItem::CELL_MODE_CUSTOM || c.mode == TreeItem::CELL_MODE_ICON )) { 
				
				propagate_mouse_activated = true;
				incr_search.clear();
				return -1;
			}
			if (select_mode == SELECT_MULTI && p_mod->is_command_or_control_pressed() && c.selectable) {
				if (!c.selected || p_button == MouseButton::RIGHT) {
					p_item->select(col);
					emit_signal(SNAME("multi_selected"), p_item, col, true);