Fix bug in PNG driver triggered by https://trac.osgeo.org/grass/changeset/62026

git-svn-id: https://svn.osgeo.org/grass/grass/trunk@62036 15284696-431f-4ddb-bdfa-cd5b030d7da7

lib/pngdriver/Raster.c

@@ -122,7 +122,7 @@ int PNG_raster(int n, int row,
     int x, y;
 
     if (y1 <= y0)
-	return next_row(row, d_y0);
+	return next_row(row, d_y1);
 
     for (x = x0; x < x1; x++) {
 	int xx = dst[0][0] + x;