* pt.c (retrieve_specialization): Handle null tmpl argument.

From-SVN: r196850

gcc/cp/ChangeLog

 2013-03-20  Jason Merrill  <jason@redhat.com>
 
+	* pt.c (retrieve_specialization): Handle null tmpl argument.
+
 	PR c++/17232
 	PR c++/56642
 	* pt.c (tsubst_decl): Check return value of register_specialization.

gcc/cp/pt.c

@@ -1009,6 +1009,9 @@ optimize_specialization_lookup_p (tree tmpl)
 static tree
 retrieve_specialization (tree tmpl, tree args, hashval_t hash)
 {
+  if (tmpl == NULL_TREE)
+    return NULL_TREE;
+
   if (args == error_mark_node)
     return NULL_TREE;