Properly pass InitializationFlag back from ScriptContextTable lookups

test/mjsunit/regress/regress-crbug-633884.js

+// Copyright 2016 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+try {
+  // Leave "blarg" as the hole in a new ScriptContext.
+  Realm.eval(Realm.current(), "throw Error(); let blarg");
+} catch (e) { }
+
+// Access "blarg" via a dynamic lookup. Should not crash!
+assertThrows(function() {
+  // Prevent full-codegen from optimizing away the %LoadLookupSlot call.
+  eval("var x = 5");
+  blarg;
+});