### 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_icon("radio_checked", "PopupMenu", icons["radio_checked"]);
	theme->set_icon("radio_checked_disabled", "PopupMenu", icons["radio_checked"]);
	theme->set_icon("radio_unchecked", "PopupMenu", icons["radio_unchecked"]);
	theme->set_icon("radio_unchecked_disabled", "PopupMenu", icons["radio_unchecked"]);
	theme->set_icon("submenu", "PopupMenu", icons["popup_menu_arrow_right"]);
	theme->set_icon("submenu_mirrored", "PopupMenu", icons["popup_menu_arrow_left"]);
	theme->set_font("font", "PopupMenu", Ref<Font>());
	theme->set_font("font_separator", "PopupMenu", Ref<Font>());
	theme->set_font_size("font_size", "PopupMenu", -1);
	theme->set_font_size("font_separator_size", "PopupMenu", -1);
	theme->set_color("font_color", "PopupMenu", control_font_color);
	theme->set_color("font_accelerator_color", "PopupMenu", Color(0.7, 0.7, 0.7, 0.8));
	theme->set_color("font_disabled_color", "PopupMenu", Color(0.4, 0.4, 0.4, 0.8));
	theme->set_color("font_hover_color", "PopupMenu", control_font_color);
	theme->set_color("font_separator_color", "PopupMenu", control_font_color);
	theme->set_color("font_outline_color", "PopupMenu", Color(1, 1, 1));
	theme->set_color("font_separator_outline_color", "PopupMenu", Color(1, 1, 1));
	theme->set_constant("indent", "PopupMenu", 10 * scale);
	theme->set_constant("h_separation", "PopupMenu", 4 * scale);
	theme->set_constant("v_separation", "PopupMenu", 4 * scale);
	theme->set_constant("outline_size", "PopupMenu", 0);
	theme->set_constant("separator_outline_size", "PopupMenu", 0);
	theme->set_constant("item_start_padding", "PopupMenu", 2 * scale);
	theme->set_constant("item_end_padding", "PopupMenu", 2 * scale);
	
	Ref<StyleBoxFlat> graphnode_normal = make_flat_stylebox(style_normal_color, 18, 42, 18, 12);
	graphnode_normal->set_border_width(SIDE_TOP, 30);
	graphnode_normal->set_border_color(Color(0.325, 0.325, 0.325, 0.6));
	Ref<StyleBoxFlat> graphnode_selected = graphnode_normal->duplicate();
	graphnode_selected->set_border_color(Color(0.625, 0.625, 0.625, 0.6));