### 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("line_length_guideline_color", "CodeEdit", Color(0.3, 0.5, 0.8, 0.1));
	theme->set_color("search_result_color", "CodeEdit", Color(0.3, 0.3, 0.3));
	theme->set_color("search_result_border_color", "CodeEdit", Color(0.3, 0.3, 0.3, 0.4));
	theme->set_constant("completion_lines", "CodeEdit", 7);
	theme->set_constant("completion_max_width", "CodeEdit", 50);
	theme->set_constant("completion_scroll_width", "CodeEdit", 6);
	theme->set_constant("line_spacing", "CodeEdit", 4 * scale);
	theme->set_constant("outline_size", "CodeEdit", 0);
	Ref<Texture2D> empty_icon = memnew(ImageTexture);
	const Ref<StyleBoxFlat> style_scrollbar = make_flat_stylebox(style_normal_color, 4, 4, 4, 4, 10);
	Ref<StyleBoxFlat> style_scrollbar_grabber = make_flat_stylebox(style_progress_color, 4, 4, 4, 4, 10);
	Ref<StyleBoxFlat> style_scrollbar_grabber_highlight = make_flat_stylebox(style_focus_color, 4, 4, 4, 4, 10);
	Ref<StyleBoxFlat> style_scrollbar_grabber_pressed = make_flat_stylebox(style_focus_color * Color(0.75, 0.75, 0.75), 4, 4, 4, 4, 10);
	
	theme->set_stylebox("scroll", "HScrollBar", style_scrollbar);
	theme->set_stylebox("scroll_focus", "HScrollBar", focus);
	theme->set_stylebox("grabber", "HScrollBar", style_scrollbar_grabber);
	theme->set_stylebox("grabber_highlight", "HScrollBar", style_scrollbar_grabber_highlight);
	theme->set_stylebox("grabber_pressed", "HScrollBar", style_scrollbar_grabber_pressed);
	theme->set_icon("increment", "HScrollBar", empty_icon);
	theme->set_icon("increment_highlight", "HScrollBar", empty_icon);
	theme->set_icon("increment_pressed", "HScrollBar", empty_icon);
	theme->set_icon("decrement", "HScrollBar", empty_icon);
	theme->set_icon("decrement_highlight", "HScrollBar", empty_icon);
	theme->set_icon("decrement_pressed", "HScrollBar", empty_icon);
	
	theme->set_stylebox("scroll", "VScrollBar", style_scrollbar);
	theme->set_stylebox("scroll_focus", "VScrollBar", focus);
	theme->set_stylebox("grabber", "VScrollBar", style_scrollbar_grabber);
	theme->set_stylebox("grabber_highlight", "VScrollBar", style_scrollbar_grabber_highlight);