Yet another "set thread pointer to NULL during thread run" fix.
diff --git a/isisd/isis_adjacency.c b/isisd/isis_adjacency.c
index de74769..d11e32e 100644
--- a/isisd/isis_adjacency.c
+++ b/isisd/isis_adjacency.c
@@ -277,6 +277,7 @@
   adj = THREAD_ARG (thread);
   assert (adj);
   level = adj->level;
+  adj->t_expire = NULL;
 
   /* trigger the adj expire event */
   isis_adj_state_change (adj, ISIS_ADJ_DOWN, "holding time expired");