### 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("relationship_line_color", "Tree", Color(0.27, 0.27, 0.27));
	theme->set_color("parent_hl_line_color", "Tree", Color(0.27, 0.27, 0.27));
	theme->set_color("children_hl_line_color", "Tree", Color(0.27, 0.27, 0.27));
	theme->set_color("custom_button_font_highlight", "Tree", control_font_hover_color);
	theme->set_constant("h_separation", "Tree", 4 * scale);
	theme->set_constant("v_separation", "Tree", 4 * scale);
	theme->set_constant("item_margin", "Tree", 16 * scale);
	theme->set_constant("button_margin", "Tree", 4 * scale);
	theme->set_constant("draw_relationship_lines", "Tree", 0);
	theme->set_constant("relationship_line_width", "Tree", 1);
	theme->set_constant("parent_hl_line_width", "Tree", 1);
	theme->set_constant("children_hl_line_width", "Tree", 1);
	theme->set_constant("parent_hl_line_margin", "Tree", 0);
	theme->set_constant("draw_guides", "Tree", 1);
	theme->set_constant("scroll_border", "Tree", 4);
	theme->set_constant("scroll_speed", "Tree", 12);
	theme->set_constant("outline_size", "Tree", 0);
	
	theme->set_stylebox("panel", "ItemList", make_flat_stylebox(style_normal_color));
	theme->set_stylebox("focus", "ItemList", focus);
	theme->set_constant("h_separation", "ItemList", 4);
	theme->set_constant("v_separation", "ItemList", 2);
	theme->set_constant("icon_margin", "ItemList", 4);
	theme->set_constant("line_separation", "ItemList", 2 * scale);
	theme->set_font("font", "ItemList", Ref<Font>());
	theme->set_font_size("font_size", "ItemList", -1);
	theme->set_color("font_color", "ItemList", control_font_lower_color);
	theme->set_color("font_selected_color", "ItemList", control_font_pressed_color);
	theme->set_color("font_outline_color", "ItemList", Color(1, 1, 1));
	theme->set_color("guide_color", "ItemList", Color(0.7, 0.7, 0.7, 0.25));