missing malloc() return check in athn(4)

[Stefan Sperling]

I added this bug recently...

Index: athn.c
===================================================================
RCS file: /cvs/src/sys/dev/ic/athn.c,v
retrieving revision 1.95
diff -u -p -r1.95 athn.c
--- athn.c      12 Jan 2017 18:06:57 -0000      1.95
+++ athn.c      17 Jan 2017 19:33:31 -0000
@@ -2337,7 +2337,7 @@ athn_node_alloc(struct ieee80211com *ic)
        struct athn_node *an;
 
        an = malloc(sizeof(struct athn_node), M_DEVBUF, M_NOWAIT | M_ZERO);
-       if (ic->ic_flags & IEEE80211_F_HTON)
+       if (an && (ic->ic_flags & IEEE80211_F_HTON))
                ieee80211_mira_node_init(&an->mn);
        return (struct ieee80211_node *)an;
 }