### 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_constant("separation", "VSplitContainer", 12 * scale);
	theme->set_constant("minimum_grab_thickness", "SplitContainer", 6 * scale);
	theme->set_constant("minimum_grab_thickness", "HSplitContainer", 6 * scale);
	theme->set_constant("minimum_grab_thickness", "VSplitContainer", 6 * scale);
	theme->set_constant("autohide", "SplitContainer", 1 * scale);
	theme->set_constant("autohide", "HSplitContainer", 1 * scale);
	theme->set_constant("autohide", "VSplitContainer", 1 * scale);
	theme->set_constant("h_separation", "FlowContainer", 4 * scale);
	theme->set_constant("v_separation", "FlowContainer", 4 * scale);
	theme->set_constant("h_separation", "HFlowContainer", 4 * scale);
	theme->set_constant("v_separation", "HFlowContainer", 4 * scale);
	theme->set_constant("h_separation", "VFlowContainer", 4 * scale);
	theme->set_constant("v_separation", "VFlowContainer", 4 * scale);
	theme->set_stylebox("panel", "PanelContainer", make_flat_stylebox(style_normal_color, 0, 0, 0, 0));
	theme->set_icon("minus", "GraphEdit", icons["zoom_less"]);
	theme->set_icon("reset", "GraphEdit", icons["zoom_reset"]);
	theme->set_icon("more", "GraphEdit", icons["zoom_more"]);
	theme->set_icon("snap", "GraphEdit", icons["grid_snap"]);
	theme->set_icon("minimap", "GraphEdit", icons["grid_minimap"]);
	theme->set_icon("layout", "GraphEdit", icons["grid_layout"]);
	theme->set_stylebox("bg", "GraphEdit", make_flat_stylebox(style_normal_color, 4, 4, 4, 5));
	theme->set_color("grid_minor", "GraphEdit", Color(1, 1, 1, 0.05));
	theme->set_color("grid_major", "GraphEdit", Color(1, 1, 1, 0.2));
	theme->set_color("selection_fill", "GraphEdit", Color(1, 1, 1, 0.3));
	theme->set_color("selection_stroke", "GraphEdit", Color(1, 1, 1, 0.8));
	theme->set_color("activity", "GraphEdit", Color(1, 1, 1));
	
	theme->set_constant("port_hotzone_inner_extent", "GraphEdit", 22 * scale);
	theme->set_constant("port_hotzone_outer_extent", "GraphEdit", 26 * scale);
	theme->set_stylebox("bg", "GraphEditMinimap", make_flat_stylebox(Color(0.24, 0.24, 0.24), 0, 0, 0, 0));