Fix `VSlider` grabber area.

scene/gui/slider.cpp

@@ -275,7 +275,7 @@ void Slider::_notification(int p_what) {
 				double areasize = size.height - (theme_cache.center_grabber ? 0 : grabber->get_height());
 				int grabber_shift = theme_cache.center_grabber ? grabber->get_height() / 2 : 0;
 				style->draw(ci, Rect2i(Point2i(size.width / 2 - widget_width / 2, 0), Size2i(widget_width, size.height)));
-				grabber_area->draw(ci, Rect2i(Point2i((size.width - widget_width) / 2, size.height - areasize * ratio - grabber->get_height() / 2 + grabber_shift), Size2i(widget_width, areasize * ratio + grabber->get_height() / 2 - grabber_shift)));
+				grabber_area->draw(ci, Rect2i(Point2i((size.width - widget_width) / 2, Math::round(size.height - areasize * ratio - grabber->get_height() / 2 + grabber_shift)), Size2i(widget_width, Math::round(areasize * ratio + grabber->get_height() / 2 - grabber_shift))));
 
 				if (ticks > 1) {
 					int grabber_offset = (grabber->get_height() / 2 - tick->get_height() / 2);