### 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->is_visible()) {
		return 0;
	}
	int height = compute_item_height(p_item);
	height += theme_cache.v_separation;
	if (!p_item->collapsed) { 
		TreeItem *c = p_item->first_child;
		while (c) {
			height += get_item_height(c);
			c = c->next;
		}
	}
	return height;
}
void Tree::draw_item_rect(TreeItem::Cell &p_cell, const Rect2i &p_rect, const Color &p_color, const Color &p_icon_color, int p_ol_size, const Color &p_ol_color) {
	ERR_FAIL_COND(theme_cache.font.is_null());
	Rect2i rect = p_rect;
	Size2 ts = p_cell.text_buf->get_size();
	bool rtl = is_layout_rtl();
	int w = 0;