### Godot version

4.x (beta 5, 6, 7, 8, 9, 10) didn't tested versions before beta 5
Also reproducable in current master: c5bfe13
  
### System information

Windows 10

### Issue description

When clicking around the bottom edge of the scrollbar grabber, it is not detected as such and instead jumps to a lower position, as if you click on the free area of the scrollbar.

The red marked area is not detected as grabber click. Everything is fine on the top edge.
![image](https://user-images.githubusercontent.com/66004280/210325316-6718b793-b3ec-4c3a-b2b3-0df0f431a222.png)

### Steps to reproduce

Just use a `ScrollContainer` with e.g. a `VBox` and many `Button`s.

See the video:

https://user-images.githubusercontent.com/66004280/210325006-718e0f57-49b3-4aa1-ad35-653b9c66d9fa.mp4

### Minimal reproduction project

N/A
const Color style_pressed_color = Color(0, 0, 0, 0.6);
	const Color style_disabled_color = Color(0.1, 0.1, 0.1, 0.3);
	const Color style_focus_color = Color(1, 1, 1, 0.75);
	const Color style_popup_color = Color(0.25, 0.25, 0.25, 1);
	const Color style_popup_border_color = Color(0.175, 0.175, 0.175, 1);
	const Color style_popup_hover_color = Color(0.4, 0.4, 0.4, 1);
	const Color style_selected_color = Color(1, 1, 1, 0.3);
	
	const Color style_progress_color = Color(1, 1, 1, 0.4);
	const Color style_separator_color = Color(0.5, 0.5, 0.5);
	
	
	Dictionary icons;
	for (int i = 0; i < default_theme_icons_count; i++) {
		icons[default_theme_icons_names[i]] = generate_icon(i);
	}
	
	theme->set_stylebox("panel", "Panel", make_flat_stylebox(style_normal_color, 0, 0, 0, 0));
	
	const Ref<StyleBoxFlat> button_normal = make_flat_stylebox(style_normal_color);
	const Ref<StyleBoxFlat> button_hover = make_flat_stylebox(style_hover_color);
	const Ref<StyleBoxFlat> button_pressed = make_flat_stylebox(style_pressed_color);
	const Ref<StyleBoxFlat> button_disabled = make_flat_stylebox(style_disabled_color);
	Ref<StyleBoxFlat> focus = make_flat_stylebox(style_focus_color, default_margin, default_margin, default_margin, default_margin, default_corner_radius, false, 2);
	
	focus->set_expand_margin_size_all(2 * scale);
	theme->set_stylebox("normal", "Button", button_normal);
	theme->set_stylebox("hover", "Button", button_hover);
	theme->set_stylebox("pressed", "Button", button_pressed);
	theme->set_stylebox("disabled", "Button", button_disabled);