### 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
v_scroll->set_value(drag_from + drag_accum);
			drag_speed = -mm->get_velocity().y;
		}
	}
	Ref<InputEventMouseButton> mb = p_event;
	if (mb.is_valid()) {
		bool rtl = is_layout_rtl();
		if (!mb->is_pressed()) {
			if (mb->get_button_index() == MouseButton::LEFT ||
					mb->get_button_index() == MouseButton::RIGHT) {
				Point2 pos = mb->get_position();
				if (rtl) {
					pos.x = get_size().width - pos.x;
				}
				pos -= theme_cache.panel_style->get_offset();
				if (show_column_titles) {
					pos.y -= _get_title_button_height();
					if (pos.y < 0) {
						pos.x += theme_cache.offset.x;
						int len = 0;
						for (int i = 0; i < columns.size(); i++) {
							len += get_column_width(i);
							if (pos.x < static_cast<real_t>(len)) {
								emit_signal(SNAME("column_title_clicked"), i, mb->get_button_index());
								break;
							}
						}
					}
				}
			}