### 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
prev_hl_ofs = root_pos.y + Math::floor(parent_line_width / 2);
						} else {
							if (htotal >= 0) {
								RenderingServer::get_singleton()->canvas_item_add_line(ci, root_pos, Point2i(parent_pos.x + Math::floor(children_line_width / 2), root_pos.y), theme_cache.children_hl_line_color, children_line_width);
							}
							RenderingServer::get_singleton()->canvas_item_add_line(ci, Point2i(parent_pos.x, root_pos.y + Math::floor(children_line_width / 2)), Point2i(parent_pos.x, prev_ofs + Math::floor(children_line_width / 2)), theme_cache.children_hl_line_color, children_line_width);
						}
					} else {
						
						
						if (_is_sibling_branch_selected(c)) {
							if (htotal >= 0) {
								RenderingServer::get_singleton()->canvas_item_add_line(ci, root_pos, Point2i(parent_pos.x + theme_cache.parent_hl_line_margin, root_pos.y), theme_cache.relationship_line_color, line_width);
							}
							RenderingServer::get_singleton()->canvas_item_add_line(ci, Point2i(parent_pos.x, root_pos.y + Math::floor(parent_line_width / 2)), Point2i(parent_pos.x, prev_hl_ofs), theme_cache.parent_hl_line_color, parent_line_width);
							prev_hl_ofs = root_pos.y + Math::floor(parent_line_width / 2);
						} else {
							if (htotal >= 0) {
								RenderingServer::get_singleton()->canvas_item_add_line(ci, root_pos, Point2i(parent_pos.x + Math::floor(line_width / 2), root_pos.y), theme_cache.relationship_line_color, line_width);
							}
							RenderingServer::get_singleton()->canvas_item_add_line(ci, Point2i(parent_pos.x, root_pos.y + Math::floor(line_width / 2)), Point2i(parent_pos.x, prev_ofs + Math::floor(line_width / 2)), theme_cache.relationship_line_color, line_width);
						}
					}
				}
				prev_ofs = root_pos.y + more_prev_ofs;
			}
			if (child_h < 0) {
				if (htotal == -1) {
					break; 
				}