d.histogram: fix tick labels, see https://trac.osgeo.org/grass/ticket/2463, author Adam Laza

git-svn-id: https://svn.osgeo.org/grass/grass/trunk@68488 15284696-431f-4ddb-bdfa-cd5b030d7da7

display/d.histogram/bar.c

@@ -307,6 +307,7 @@ int bar(struct stat_list *dist_stats,	/* list of distribution statistics */
 	    if (nodata && i == dist_stats->mincat)
 		sprintf(txt, "null");
 	    else if (is_fp) {
+		dmin = range_dmin + i * (range_dmax - range_dmin) / nsteps;
 		if ((range_dmax - range_dmin) <= 1.0)
 		    sprintf(txt, "%.2f", dmin / (double)tic_unit);
 		else