proc.c: check iseq before replication

* proc.c (proc_binding): do not replicate when iseq not found as
  rb_method_get_iseq() can return NULL.
  [ruby-core:68673] [Bug #11012]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@50112 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

proc.c

@@ -2507,7 +2507,7 @@ proc_binding(VALUE self)
 	}
 	iseq = rb_method_get_iseq((VALUE)((struct vm_ifunc *)iseq)->data);
 	GetEnvPtr(envval, env);
-	if (env->local_size < iseq->local_size) {
+	if (iseq && env->local_size < iseq->local_size) {
 	    int prev_local_size = env->local_size;
 	    int local_size = iseq->local_size;
 	    VALUE newenvval = TypedData_Wrap_Struct(RBASIC_CLASS(envval), RTYPEDDATA_TYPE(envval), 0);