### 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
p_item->cells[i].text_buf->draw(ci, text_pos + Vector2(cell_width - text_width, 0), col);
						} else {
							if (outline_size > 0 && font_outline_color.a > 0) {
								p_item->cells[i].text_buf->draw_outline(ci, text_pos, outline_size, font_outline_color);
							}
							p_item->cells[i].text_buf->draw(ci, text_pos, col);
						}
						if (!p_item->cells[i].editable) {
							break;
						}
						Point2i updown_pos = item_rect.position;
						updown_pos.x += item_rect.size.x - updown->get_width();
						updown_pos.y += Math::floor(((item_rect.size.y - updown->get_height())) / 2.0);
						updown->draw(ci, updown_pos);
					}
				} break;
				case TreeItem::CELL_MODE_ICON: {
					if (p_item->cells[i].icon.is_null()) {
						break;
					}
					Size2i icon_size = p_item->cells[i].get_icon_size();
					if (p_item->cells[i].icon_max_w > 0 && icon_size.width > p_item->cells[i].icon_max_w) {
						icon_size.height = icon_size.height * p_item->cells[i].icon_max_w / icon_size.width;
						icon_size.width = p_item->cells[i].icon_max_w;
					}
					Point2i icon_ofs = (item_rect.size - icon_size) / 2;
					icon_ofs += item_rect.position;
					draw_texture_rect(p_item->cells[i].icon, Rect2(icon_ofs, icon_size), false, icon_col);
				} break;
				case TreeItem::CELL_MODE_CUSTOM: {