### 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("file_icon_color", "FileDialog", Color(1, 1, 1));
	theme->set_color("file_disabled_color", "FileDialog", Color(1, 1, 1, 0.25));
	
	theme->set_stylebox("panel", "PopupPanel", make_flat_stylebox(style_normal_color));
	
	theme->set_stylebox("panel", "PopupDialog", make_flat_stylebox(style_normal_color));
	
	Ref<StyleBoxLine> separator_horizontal = memnew(StyleBoxLine);
	separator_horizontal->set_thickness(Math::round(scale));
	separator_horizontal->set_color(style_separator_color);
	separator_horizontal->set_default_margin_individual(default_margin, 0, default_margin, 0);
	Ref<StyleBoxLine> separator_vertical = separator_horizontal->duplicate();
	separator_vertical->set_vertical(true);
	separator_vertical->set_default_margin_individual(0, default_margin, 0, default_margin);
	
	Ref<StyleBoxFlat> style_popup_panel = make_flat_stylebox(style_popup_color);
	style_popup_panel->set_border_width_all(2);
	style_popup_panel->set_border_color(style_popup_border_color);
	Ref<StyleBoxFlat> style_popup_panel_disabled = style_popup_panel->duplicate();
	style_popup_panel_disabled->set_bg_color(style_disabled_color);
	theme->set_stylebox("panel", "PopupMenu", style_popup_panel);
	theme->set_stylebox("panel_disabled", "PopupMenu", style_popup_panel_disabled);
	theme->set_stylebox("hover", "PopupMenu", make_flat_stylebox(style_popup_hover_color));
	theme->set_stylebox("separator", "PopupMenu", separator_horizontal);
	theme->set_stylebox("labeled_separator_left", "PopupMenu", separator_horizontal);
	theme->set_stylebox("labeled_separator_right", "PopupMenu", separator_horizontal);
	theme->set_icon("checked", "PopupMenu", icons["checked"]);
	theme->set_icon("checked_disabled", "PopupMenu", icons["checked"]);
	theme->set_icon("unchecked", "PopupMenu", icons["unchecked"]);
	theme->set_icon("unchecked_disabled", "PopupMenu", icons["unchecked"]);