### 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->set_range(col, c.val + (up ? 1.0 : -1.0) * c.step);
							item_edited(col, p_item, p_button);
						} else if (p_button == MouseButton::RIGHT) {
							p_item->set_range(col, (up ? c.max : c.min));
							item_edited(col, p_item, p_button);
						} else if (p_button == MouseButton::WHEEL_UP) {
							p_item->set_range(col, c.val + c.step);
							item_edited(col, p_item, p_button);
						} else if (p_button == MouseButton::WHEEL_DOWN) {
							p_item->set_range(col, c.val - c.step);
							item_edited(col, p_item, p_button);
						}
						
						bring_up_editor = false;
					} else {
						editor_text = String::num(p_item->cells[col].val, Math::range_step_decimals(p_item->cells[col].step));
						if (select_mode == SELECT_MULTI && get_viewport()->get_processed_events_count() == focus_in_id) {
							bring_up_editor = false;
						}
					}
				}
				click_handled = true;
			} break;
			case TreeItem::CELL_MODE_ICON: {
				bring_up_editor = false;
			} break;
			case TreeItem::CELL_MODE_CUSTOM: {
				edited_item = p_item;
				edited_col = col;
				bool on_arrow = x > col_width - theme_cache.select_arrow->get_width();