Fix crash if fnext/fprev are given an empty folder list

Add a check for a NULL pointer, which stops fnext/fprev
from segfaulting if given an empty folder list (for example
via 'fnext -folders emptyfile').

Signed-off-by: Peter Maydell <pmaydell@chiark.greenend.org.uk>

diff --git a/uip/new.c b/uip/new.c
index 41d2ebf..254950b 100644 (file)
--- a/uip/new.c
+++ b/uip/new.c
@@ -308,7 +308,10 @@ doit(char *cur, char *folders, char *sequences[])
                  folders, sequences);
 
     if (run_mode == FNEXT || run_mode == FPREV) {
-       if (first->n_next == NULL) {
+       if (first == NULL) {
+           /* No folders at all... */
+           return NULL;
+       } else if (first->n_next == NULL) {
            /* We have only one node; any desired messages in it? */
            if (first->n_field == NULL) {
                return NULL;