Fix null-equality comparison for unoptimized branch code.

tests/language/equality_test.dart

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 
 class A {
   bool _result;
   A(this._result);
   operator ==(x) { return _result; }
 }
@@ skipping 22 matching lines @@
   Expect.isTrue(null == null);
   Expect.isFalse(null != null);
   
   Expect.throws(() => death() == 5);
   Expect.isFalse(death() == nullFn());
   Expect.isFalse(nullFn() == death());
   Expect.isTrue(nullFn() == nullFn());
   Expect.isTrue(death() != nullFn());
   Expect.isTrue(nullFn() != death());
   Expect.isFalse(nullFn() != nullFn());
+
+  if (death() == nullFn()) {
+    throw "failed";
+  }
+  if (death() != nullFn()) {
+  } else {
+    throw "failed";
+  }
 }
 
 main() {
   for (int i = 0; i < 1000; i++) tests();
 }