virt-alignment-scan: Add checks for when API calls return NULL.

In particular, virt-alignment-scan -a /dev/null would segfault
because of an error returned by parted.
(cherry picked from commit 7b192f5a672197ad67ac23501e420c674aa2f3a9)

diff --git a/align/scan.c b/align/scan.c
index 529add5..7b4631a 100644 (file)
--- a/align/scan.c
+++ b/align/scan.c
@@ -228,9 +228,13 @@ scan (void)
   struct guestfs_partition_list *parts;
 
   devices = guestfs_list_devices (g);
+  if (devices == NULL)
+    exit (EXIT_FAILURE);
 
   for (i = 0; devices[i] != NULL; ++i) {
     parts = guestfs_part_list (g, devices[i]);
+    if (parts == NULL)
+      exit (EXIT_FAILURE);
 
     /* Canonicalize the name of the device for printing. */
     if (STRPREFIX (devices[i], "/dev/") &&