### 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
if (p_item->cells[i].expand_right) {
				int plus = 1;
				while (i + plus < columns.size() && !p_item->cells[i + plus].editable && p_item->cells[i + plus].mode == TreeItem::CELL_MODE_STRING && p_item->cells[i + plus].text.is_empty() && p_item->cells[i + plus].icon.is_null()) {
					col_width += theme_cache.h_separation;
					col_width += get_column_width(i + plus);
					plus++;
				}
			}
			if (x > col_width) {
				col_ofs += col_width;
				x -= col_width;
				limit_w -= col_width;
				continue;
			}
			col = i;
			break;
		}
		if (col == -1) {
			return -1;
		} else if (col == 0) {
			int margin = x_ofs + theme_cache.item_margin; 
			
			col_width -= margin;
			limit_w -= margin;
			col_ofs += margin;
			x -= margin;
		} else {
			col_width -= theme_cache.h_separation;
			limit_w -= theme_cache.h_separation;
			x -= theme_cache.h_separation;