sna: Perform an explicit check against the region extents

RegionNotEmpty() is only valid if we only use the Region API, and as we
mix direct operations on the region extents, we need to also do our own
final check.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>

src/sna/sna_accel.c

@@ -5582,7 +5582,7 @@ sna_do_copy(DrawablePtr src, DrawablePtr dst, GCPtr gc,
 	     region.extents.x2, region.extents.y2,
 	     (long)RegionNumRects(&region)));
 
-	if (RegionNotEmpty(&region))
+	if (!box_empty(&region.extents))
 		copy(src, dst, gc, &region, sx-dx, sy-dy, bitPlane, closure);
 	RegionUninit(&region);