Fix crash at start up with conf-dir=/path,*

Thanks to Brian Carpenter and American Fuzzy Lop for finding the bug.

src/option.c

@@ -1514,12 +1514,18 @@ static int one_opt(int option, char *arg, char *errstr, char *gen_err, int comma
 	      {
 		li = opt_malloc(sizeof(struct list));
 		if (*arg == '*')
+		  {
+		    /* "*" with no suffix is a no-op */
+		    if (arg[1] == 0)
+		      free(li);
+		    else
 		      {
 			li->next = match_suffix;
 			match_suffix = li;
 			/* Have to copy: buffer is overwritten */
 			li->suffix = opt_string_alloc(arg+1);
 		      }
+		  }
 		else
 		  {
 		    li->next = ignore_suffix;