### 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
PackedColorArray colors;
		colors.resize(precision);
		for (int i = 0; i < precision; i++) {
			float h = i / float(precision - 1);
			offsets.write[i] = h;
			colors.write[i] = Color::from_hsv(h, 1, 1);
		}
		hue_gradient->set_offsets(offsets);
		hue_gradient->set_colors(colors);
		Ref<GradientTexture2D> hue_texture;
		hue_texture.instantiate();
		hue_texture->set_width(800);
		hue_texture->set_height(6);
		hue_texture->set_gradient(hue_gradient);
		theme->set_icon("color_hue", "ColorPicker", hue_texture);
	}
	{
		const int precision = 7;
		Ref<Gradient> hue_gradient;
		hue_gradient.instantiate();
		PackedFloat32Array offsets;
		offsets.resize(precision);
		PackedColorArray colors;
		colors.resize(precision);
		for (int i = 0; i < precision; i++) {
			float h = i / float(precision - 1);
			offsets.write[i] = h;
			colors.write[i] = Color::from_ok_hsl(h, 1, 0.5);
		}
		hue_gradient->set_offsets(offsets);