### 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
TreeItem *next = selected_item->get_first_child();
			while (next && next != selected_item->next) {
				next->set_collapsed(true);
				next = next->get_next_visible();
			}
		} else {
			_go_left();
		}
	} else if (p_event->is_action("ui_up", true) && p_event->is_pressed() && !is_command) {
		if (!cursor_can_exit_tree) {
			accept_event();
		}
		_go_up();
	} else if (p_event->is_action("ui_down", true) && p_event->is_pressed() && !is_command) {
		if (!cursor_can_exit_tree) {
			accept_event();
		}
		_go_down();
	} else if (p_event->is_action("ui_page_down", true) && p_event->is_pressed()) {
		if (!cursor_can_exit_tree) {
			accept_event();
		}
		TreeItem *next = nullptr;
		if (!selected_item) {
			return;
		}
		next = selected_item;
		for (int i = 0; i < 10; i++) {
			TreeItem *_n = next->get_next_visible();
			if (_n) {