### 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_outline_color", "CheckButton", Color(1, 1, 1));
	theme->set_constant("h_separation", "CheckButton", 4 * scale);
	theme->set_constant("check_v_offset", "CheckButton", 0 * scale);
	theme->set_constant("outline_size", "CheckButton", 0);
	
	theme->set_stylebox("normal", "Label", memnew(StyleBoxEmpty));
	theme->set_font("font", "Label", Ref<Font>());
	theme->set_font_size("font_size", "Label", -1);
	theme->set_color("font_color", "Label", Color(1, 1, 1));
	theme->set_color("font_shadow_color", "Label", Color(0, 0, 0, 0));
	theme->set_color("font_outline_color", "Label", Color(1, 1, 1));
	theme->set_constant("shadow_offset_x", "Label", 1 * scale);
	theme->set_constant("shadow_offset_y", "Label", 1 * scale);
	theme->set_constant("outline_size", "Label", 0);
	theme->set_constant("shadow_outline_size", "Label", 1 * scale);
	theme->set_constant("line_spacing", "Label", 3 * scale);
	theme->set_type_variation("HeaderSmall", "Label");
	theme->set_font_size("font_size", "HeaderSmall", default_font_size + 4);
	theme->set_type_variation("HeaderMedium", "Label");
	theme->set_font_size("font_size", "HeaderMedium", default_font_size + 8);
	theme->set_type_variation("HeaderLarge", "Label");
	theme->set_font_size("font_size", "HeaderLarge", default_font_size + 12);
	
	Ref<StyleBoxFlat> style_line_edit = make_flat_stylebox(style_normal_color);
	
	style_line_edit->set_border_width(SIDE_BOTTOM, 2);
	style_line_edit->set_border_color(style_pressed_color);
	theme->set_stylebox("normal", "LineEdit", style_line_edit);
	theme->set_stylebox("focus", "LineEdit", focus);
	Ref<StyleBoxFlat> style_line_edit_read_only = make_flat_stylebox(style_disabled_color);