### 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
int len = 0;
				for (int i = 0; i < columns.size(); i++) {
					len += get_column_width(i);
					if (pos.x < len) {
						cache.hover_type = Cache::CLICK_TITLE;
						cache.hover_index = i;
						break;
					}
				}
			}
		}
		if (root) {
			Point2 mpos = mm->get_position();
			if (rtl) {
				mpos.x = get_size().width - mpos.x;
			}
			mpos -= theme_cache.panel_style->get_offset();
			mpos.y -= _get_title_button_height();
			if (mpos.y >= 0) {
				if (h_scroll->is_visible_in_tree()) {
					mpos.x += h_scroll->get_value();
				}
				if (v_scroll->is_visible_in_tree()) {
					mpos.y += v_scroll->get_value();
				}
				TreeItem *old_it = cache.hover_item;
				int old_col = cache.hover_cell;
				int col, h, section;
				TreeItem *it = _find_item_at_pos(root, mpos, col, h, section);
				if (drop_mode_flags) {