### 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
custom_popup_rect = Rect2i(get_global_position() + Point2i(col_ofs, _get_title_button_height() + y_ofs + item_h - theme_cache.offset.y), Size2(get_column_width(col), item_h));
				if (on_arrow || !p_item->cells[col].custom_button) {
					emit_signal(SNAME("custom_popup_edited"), ((bool)(x >= (col_width - item_h / 2))));
				}
				if (!p_item->cells[col].custom_button || !on_arrow) {
					item_edited(col, p_item, p_button);
				}
				click_handled = true;
				return -1;
			} break;
		};
		if (!bring_up_editor || p_button != MouseButton::LEFT) {
			return -1;
		}
		click_handled = true;
		popup_pressing_edited_item = p_item;
		popup_pressing_edited_item_column = col;
		pressing_item_rect = Rect2(get_global_position() + Point2i(col_ofs, _get_title_button_height() + y_ofs) - theme_cache.offset, Size2(col_width, item_h));
		pressing_for_editor_text = editor_text;
		pressing_for_editor = true;
		return -1; 
	} else {
		Point2i new_pos = p_pos;
		if (!skip) {
			x_ofs += theme_cache.item_margin;
			
			y_ofs += item_h;
			new_pos.y -= item_h;
		}
		if (!p_item->collapsed) {