vm.c: check TOPLEVEL_BINDING

* vm.c (vm_set_main_stack): TOPLEVEL_BINDING must be built.
  http://www.viva64.com/en/b/0414/#ID0EQ1CI  [ruby-core:76973]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@55964 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

ChangeLog

@@ -1,3 +1,8 @@
+Fri Aug 19 09:12:45 2016  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* vm.c (vm_set_main_stack): TOPLEVEL_BINDING must be built.
+	  http://www.viva64.com/en/b/0414/#ID0EQ1CI  [ruby-core:76973]
+
 Fri Aug 19 01:00:53 2016  Yuichiro Kaneko  <yui-knk@ruby-lang.org>
 
 	* proc.c (mnew_missing): Remove an unused argument.

vm.c

@@ -459,11 +459,12 @@ vm_set_main_stack(rb_thread_t *th, const rb_iseq_t *iseq)
     rb_binding_t *bind;
 
     GetBindingPtr(toplevel_binding, bind);
+    RUBY_ASSERT_MESG(bind, "TOPLEVEL_BINDING is not built");
 
     vm_set_eval_stack(th, iseq, 0, &bind->block);
 
     /* save binding */
-    if (bind && iseq->body->local_table_size > 0) {
+    if (iseq->body->local_table_size > 0) {
 	vm_bind_update_env(bind, vm_make_env_object(th, th->cfp));
     }
 }