### 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
ERR_FAIL_INDEX(p_column, cells.size());
	_cell_selected(p_column);
}
void TreeItem::deselect(int p_column) {
	ERR_FAIL_INDEX(p_column, cells.size());
	_cell_deselected(p_column);
}
void TreeItem::add_button(int p_column, const Ref<Texture2D> &p_button, int p_id, bool p_disabled, const String &p_tooltip) {
	ERR_FAIL_INDEX(p_column, cells.size());
	ERR_FAIL_COND(!p_button.is_valid());
	TreeItem::Cell::Button button;
	button.texture = p_button;
	if (p_id < 0) {
		p_id = cells[p_column].buttons.size();
	}
	button.id = p_id;
	button.disabled = p_disabled;
	button.tooltip = p_tooltip;
	cells.write[p_column].buttons.push_back(button);
	cells.write[p_column].cached_minimum_size_dirty = true;
	_changed_notify(p_column);
}
int TreeItem::get_button_count(int p_column) const {