### 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
Point2 pos = p_pos;
	if ((root != p_item || !hide_root) && p_item->is_visible()) {
		h = compute_item_height(p_item) + theme_cache.v_separation;
		if (pos.y < h) {
			if (drop_mode_flags == DROP_MODE_ON_ITEM) {
				section = 0;
			} else if (drop_mode_flags == DROP_MODE_INBETWEEN) {
				section = pos.y < h / 2 ? -1 : 1;
			} else if (pos.y < h / 4) {
				section = -1;
			} else if (pos.y >= (h * 3 / 4)) {
				section = 1;
			} else {
				section = 0;
			}
			for (int i = 0; i < columns.size(); i++) {
				int w = get_column_width(i);