[PATCH] avoid NULL deref in grub_device_open

[Jim Meyering]

I ran coverity against grub.
Here's a fix for one of the things it spotted:

2011-06-11  Jim Meyering  <address@hidden>

        avoid NULL deref in grub_device_open
        * grub-core/kern/device.c (grub_device_open): Don't dereference
        a NULL pointer upon failed grub_env_get.


=== modified file 'grub-core/kern/device.c'
--- grub-core/kern/device.c     2010-09-20 19:45:06 +0000
+++ grub-core/kern/device.c     2011-06-11 06:50:02 +0000
@@ -35,7 +35,7 @@
   if (! name)
     {
       name = grub_env_get ("root");
-      if (*name == '\0')
+      if (name == NULL || *name == '\0')
        {
          grub_error (GRUB_ERR_BAD_DEVICE, "no device is set");
          goto fail;