### 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
Point2i o = Point2i(ofs + w - s.width, p_pos.y) - theme_cache.offset + p_draw_ofs;
				if (cache.click_type == Cache::CLICK_BUTTON && cache.click_item == p_item && cache.click_column == i && cache.click_index == j && !p_item->cells[i].buttons[j].disabled) {
					
					Point2 od = o;
					if (rtl) {
						od.x = get_size().width - od.x - s.x;
					}
					theme_cache.button_pressed->draw(get_canvas_item(), Rect2(od.x, od.y, s.width, MAX(s.height, label_h)));
				}
				o.y += (label_h - s.height) / 2;
				o += theme_cache.button_pressed->get_offset();
				if (rtl) {
					o.x = get_size().width - o.x - b->get_width();
				}
				b->draw(ci, o, p_item->cells[i].buttons[j].disabled ? Color(1, 1, 1, 0.5) : p_item->cells[i].buttons[j].color);
				w -= s.width + theme_cache.button_margin;
				bw += s.width + theme_cache.button_margin;
			}
			Rect2i item_rect = Rect2i(Point2i(ofs, p_pos.y) - theme_cache.offset + p_draw_ofs, Size2i(w, label_h));
			Rect2i cell_rect = item_rect;
			if (i != 0) {
				cell_rect.position.x -= theme_cache.h_separation;
				cell_rect.size.x += theme_cache.h_separation;
			}
			if (theme_cache.draw_guides) {
				Rect2 r = cell_rect;
				if (rtl) {
					r.position.x = get_size().width - r.position.x - r.size.x;
				}
				RenderingServer::get_singleton()->canvas_item_add_line(ci, Point2i(r.position.x, r.position.y + r.size.height), r.position + r.size, theme_cache.guide_color, 1);