### 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_stylebox("separator", "HSeparator", separator_horizontal);
	theme->set_stylebox("separator", "VSeparator", separator_vertical);
	theme->set_icon("close", "Icons", icons["close"]);
	theme->set_font("normal", "Fonts", Ref<Font>());
	theme->set_font("large", "Fonts", Ref<Font>());
	theme->set_constant("separation", "HSeparator", 4 * scale);
	theme->set_constant("separation", "VSeparator", 4 * scale);
	
	theme->set_constant("margin", "ColorPicker", 4 * scale);
	theme->set_constant("sv_width", "ColorPicker", 256 * scale);
	theme->set_constant("sv_height", "ColorPicker", 256 * scale);
	theme->set_constant("h_width", "ColorPicker", 30 * scale);
	theme->set_constant("label_width", "ColorPicker", 10 * scale);
	theme->set_icon("folded_arrow", "ColorPicker", icons["arrow_right"]);
	theme->set_icon("expanded_arrow", "ColorPicker", icons["arrow_down"]);
	theme->set_icon("screen_picker", "ColorPicker", icons["color_picker_pipette"]);
	theme->set_icon("shape_circle", "ColorPicker", icons["picker_shape_circle"]);
	theme->set_icon("shape_rect", "ColorPicker", icons["picker_shape_rectangle"]);
	theme->set_icon("shape_rect_wheel", "ColorPicker", icons["picker_shape_rectangle_wheel"]);
	theme->set_icon("add_preset", "ColorPicker", icons["add"]);
	theme->set_icon("sample_bg", "ColorPicker", icons["mini_checkerboard"]);
	theme->set_icon("overbright_indicator", "ColorPicker", icons["color_picker_overbright"]);
	theme->set_icon("bar_arrow", "ColorPicker", icons["color_picker_bar_arrow"]);
	theme->set_icon("picker_cursor", "ColorPicker", icons["color_picker_cursor"]);
	{
		const int precision = 7;
		Ref<Gradient> hue_gradient;
		hue_gradient.instantiate();
		PackedFloat32Array offsets;
		offsets.resize(precision);