### 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_stylebox("preset_fg", "ColorPresetButton", preset_sb);
	theme->set_icon("preset_bg", "ColorPresetButton", icons["mini_checkerboard"]);
	theme->set_icon("overbright_indicator", "ColorPresetButton", icons["color_picker_overbright"]);
	
	theme->set_stylebox("panel", "TooltipPanel",
			make_flat_stylebox(Color(0, 0, 0, 0.5), 2 * default_margin, 0.5 * default_margin, 2 * default_margin, 0.5 * default_margin));
	theme->set_font_size("font_size", "TooltipLabel", -1);
	theme->set_font("font", "TooltipLabel", Ref<Font>());
	theme->set_color("font_color", "TooltipLabel", control_font_color);
	theme->set_color("font_shadow_color", "TooltipLabel", Color(0, 0, 0, 0));
	theme->set_color("font_outline_color", "TooltipLabel", Color(0, 0, 0, 0));
	theme->set_constant("shadow_offset_x", "TooltipLabel", 1);
	theme->set_constant("shadow_offset_y", "TooltipLabel", 1);
	theme->set_constant("outline_size", "TooltipLabel", 0);
	
	theme->set_stylebox("focus", "RichTextLabel", focus);
	theme->set_stylebox("normal", "RichTextLabel", make_empty_stylebox(0, 0, 0, 0));
	theme->set_font("normal_font", "RichTextLabel", Ref<Font>());
	theme->set_font("bold_font", "RichTextLabel", bold_font);
	theme->set_font("italics_font", "RichTextLabel", italics_font);
	theme->set_font("bold_italics_font", "RichTextLabel", bold_italics_font);
	theme->set_font("mono_font", "RichTextLabel", Ref<Font>());
	theme->set_font_size("normal_font_size", "RichTextLabel", -1);
	theme->set_font_size("bold_font_size", "RichTextLabel", -1);
	theme->set_font_size("italics_font_size", "RichTextLabel", -1);
	theme->set_font_size("bold_italics_font_size", "RichTextLabel", -1);
	theme->set_font_size("mono_font_size", "RichTextLabel", -1);
	theme->set_color("default_color", "RichTextLabel", Color(1, 1, 1));
	theme->set_color("font_selected_color", "RichTextLabel", Color(0, 0, 0, 0));
	theme->set_color("selection_color", "RichTextLabel", Color(0.1, 0.1, 1, 0.8));