### 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("font_shadow_color", "RichTextLabel", Color(0, 0, 0, 0));
	theme->set_color("font_outline_color", "RichTextLabel", Color(1, 1, 1));
	theme->set_constant("shadow_offset_x", "RichTextLabel", 1 * scale);
	theme->set_constant("shadow_offset_y", "RichTextLabel", 1 * scale);
	theme->set_constant("shadow_outline_size", "RichTextLabel", 1 * scale);
	theme->set_constant("line_separation", "RichTextLabel", 0 * scale);
	theme->set_constant("table_h_separation", "RichTextLabel", 3 * scale);
	theme->set_constant("table_v_separation", "RichTextLabel", 3 * scale);
	theme->set_constant("outline_size", "RichTextLabel", 0);
	theme->set_color("table_odd_row_bg", "RichTextLabel", Color(0, 0, 0, 0));
	theme->set_color("table_even_row_bg", "RichTextLabel", Color(0, 0, 0, 0));
	theme->set_color("table_border", "RichTextLabel", Color(0, 0, 0, 0));
	theme->set_constant("text_highlight_h_padding", "RichTextLabel", 3 * scale);
	theme->set_constant("text_highlight_v_padding", "RichTextLabel", 3 * scale);
	
	theme->set_icon("h_grabber", "SplitContainer", icons["hsplitter"]);
	theme->set_icon("v_grabber", "SplitContainer", icons["vsplitter"]);
	theme->set_icon("grabber", "VSplitContainer", icons["vsplitter"]);
	theme->set_icon("grabber", "HSplitContainer", icons["hsplitter"]);
	theme->set_constant("separation", "BoxContainer", 4 * scale);
	theme->set_constant("separation", "HBoxContainer", 4 * scale);
	theme->set_constant("separation", "VBoxContainer", 4 * scale);
	theme->set_constant("margin_left", "MarginContainer", 0 * scale);
	theme->set_constant("margin_top", "MarginContainer", 0 * scale);
	theme->set_constant("margin_right", "MarginContainer", 0 * scale);
	theme->set_constant("margin_bottom", "MarginContainer", 0 * scale);
	theme->set_constant("h_separation", "GridContainer", 4 * scale);
	theme->set_constant("v_separation", "GridContainer", 4 * scale);
	theme->set_constant("separation", "SplitContainer", 12 * scale);
	theme->set_constant("separation", "HSplitContainer", 12 * scale);