patch 8.2.4928: various white space and cosmetic mistakes

Problem:    Various white space and cosmetic mistakes.
Solution:   Change spaces to tabs, improve comments.
diff --git a/src/digraph.c b/src/digraph.c
index cfffc19..c33fc30 100644
--- a/src/digraph.c
+++ b/src/digraph.c
@@ -2337,8 +2337,9 @@
 	flag_list_all = FALSE;
     else
     {
-	int         error = FALSE;
+	int	    error = FALSE;
 	varnumber_T flag = tv_get_number_chk(&argvars[0], &error);
+
 	if (error)
 	    return;
 	flag_list_all = flag ? TRUE : FALSE;