r.watershed: skip NULL cells for streams

git-svn-id: https://svn.osgeo.org/grass/grass/trunk@56579 15284696-431f-4ddb-bdfa-cd5b030d7da7

raster/r.watershed/ram/do_cum.c

@@ -522,6 +522,7 @@ int do_cum_mfd(void)
 			swale_cells++;
 		    valued = wat[nbr_index];
 		    ele_nbr = alt[nbr_index];
+		    edge = Rast_is_c_null_value(&ele_nbr);
 		    if ((ABS(valued) + 0.5) >= threshold  &&
 		        ele_nbr > ele)
 			stream_cells++;

raster/r.watershed/seg/do_cum.c

@@ -574,6 +574,7 @@ int do_cum_mfd(void)
 
 		    /* check for swale or stream cells */
 		    is_swale = FLAG_GET(flag_nbr[ct_dir], SWALEFLAG);
+		    edge = FLAG_GET(flag_nbr[ct_dir], NULLFLAG);
 		    if (is_swale)
 			swale_cells++;
 		    if ((ABS(wat_nbr[ct_dir]) + 0.5) >= threshold &&