Fix mount -a segfault without -O, reported by Janus Troelsen.
diff --git a/lib/getmountlist.c b/lib/getmountlist.c
index c0e6875..30fb9a3 100644
--- a/lib/getmountlist.c
+++ b/lib/getmountlist.c
@@ -90,7 +90,7 @@
 {
   int i = 1;
 
-  for (;;) {
+  while (scanlist && *scanlist) {
     char *opt = comma_iterate(&scanlist, &i), *s = xstrndup(opt, i);
 
     i = comma_scan(optlist, s, 0);