### 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
theme->set_color("font_disabled_color", "MenuButton", Color(1, 1, 1, 0.3));
	theme->set_color("font_outline_color", "MenuButton", Color(1, 1, 1));
	theme->set_constant("h_separation", "MenuButton", 3 * scale);
	theme->set_constant("outline_size", "MenuButton", 0);
	
	Ref<StyleBox> cbx_empty = memnew(StyleBoxEmpty);
	cbx_empty->set_default_margin_all(4 * scale);
	Ref<StyleBox> cbx_focus = focus;
	cbx_focus->set_default_margin_all(4 * scale);
	theme->set_stylebox("normal", "CheckBox", cbx_empty);
	theme->set_stylebox("pressed", "CheckBox", cbx_empty);
	theme->set_stylebox("disabled", "CheckBox", cbx_empty);
	theme->set_stylebox("hover", "CheckBox", cbx_empty);
	theme->set_stylebox("hover_pressed", "CheckBox", cbx_empty);
	theme->set_stylebox("focus", "CheckBox", cbx_focus);
	theme->set_icon("checked", "CheckBox", icons["checked"]);
	theme->set_icon("checked_disabled", "CheckBox", icons["checked"]);
	theme->set_icon("unchecked", "CheckBox", icons["unchecked"]);
	theme->set_icon("unchecked_disabled", "CheckBox", icons["unchecked"]);
	theme->set_icon("radio_checked", "CheckBox", icons["radio_checked"]);
	theme->set_icon("radio_checked_disabled", "CheckBox", icons["radio_checked"]);
	theme->set_icon("radio_unchecked", "CheckBox", icons["radio_unchecked"]);
	theme->set_icon("radio_unchecked_disabled", "CheckBox", icons["radio_unchecked"]);
	theme->set_font("font", "CheckBox", Ref<Font>());
	theme->set_font_size("font_size", "CheckBox", -1);
	theme->set_color("font_color", "CheckBox", control_font_color);
	theme->set_color("font_pressed_color", "CheckBox", control_font_pressed_color);
	theme->set_color("font_hover_color", "CheckBox", control_font_hover_color);
	theme->set_color("font_hover_pressed_color", "CheckBox", control_font_pressed_color);
	theme->set_color("font_focus_color", "CheckBox", control_font_focus_color);