### 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
Ref<StyleBoxEmpty> empty;
	empty.instantiate();
	theme->set_stylebox("panel", "ScrollContainer", empty);
	
	theme->set_stylebox("embedded_border", "Window", sb_expand(make_flat_stylebox(style_popup_color, 10, 28, 10, 8), 8, 32, 8, 6));
	theme->set_font("title_font", "Window", Ref<Font>());
	theme->set_font_size("title_font_size", "Window", -1);
	theme->set_color("title_color", "Window", control_font_color);
	theme->set_color("title_outline_modulate", "Window", Color(1, 1, 1));
	theme->set_constant("title_outline_size", "Window", 0);
	theme->set_constant("title_height", "Window", 36 * scale);
	theme->set_constant("resize_margin", "Window", 4 * scale);
	theme->set_icon("close", "Window", icons["close"]);
	theme->set_icon("close_pressed", "Window", icons["close_hl"]);
	theme->set_constant("close_h_offset", "Window", 18 * scale);
	theme->set_constant("close_v_offset", "Window", 24 * scale);
	
	
	theme->set_stylebox("panel", "AcceptDialog", make_flat_stylebox(style_popup_color, 8 * scale, 8 * scale, 8 * scale, 8 * scale));
	theme->set_constant("buttons_separation", "AcceptDialog", 10 * scale);
	
	theme->set_icon("parent_folder", "FileDialog", icons["folder_up"]);
	theme->set_icon("back_folder", "FileDialog", icons["arrow_left"]);
	theme->set_icon("forward_folder", "FileDialog", icons["arrow_right"]);
	theme->set_icon("reload", "FileDialog", icons["reload"]);
	theme->set_icon("toggle_hidden", "FileDialog", icons["visibility_visible"]);
	theme->set_icon("folder", "FileDialog", icons["folder"]);
	theme->set_icon("file", "FileDialog", icons["file"]);
	theme->set_color("folder_icon_color", "FileDialog", Color(1, 1, 1));