Fix one missing invalid encoding case.

runtime/vm/object_test.cc

 // 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.
 
 #include "platform/globals.h"
 
 #include "vm/assembler.h"
 #include "vm/bigint_operations.h"
 #include "vm/class_finalizer.h"
 #include "vm/dart_api_impl.h"
@@ skipping 412 matching lines @@
   const String& input = String::Handle(String::New(kInput));
   const String& output = String::Handle(String::New(kOutput));
   const String& decoded = String::Handle(String::DecodeIRI(input));
   EXPECT(output.Equals(decoded));
 }
 
 
 TEST_CASE(StringDecodeIRIInvalid) {
   String& input = String::Handle();
   input = String::New("file%");
-  EXPECT(String::DecodeIRI(input) == String::null());
+  String& decoded = String::Handle();
+  decoded = String::DecodeIRI(input);
+  EXPECT(decoded.IsNull());
   input = String::New("file%3");
-  EXPECT(String::DecodeIRI(input) == String::null());
+  decoded = String::DecodeIRI(input);
+  EXPECT(decoded.IsNull());
   input = String::New("file%3g");
-  EXPECT(String::DecodeIRI(input) == String::null());
+  decoded = String::DecodeIRI(input);
+  EXPECT(decoded.IsNull());
 }
 
 
 TEST_CASE(StringIRITwoByte) {
   const intptr_t kInputLen = 3;
   const uint16_t kInput[kInputLen] = { 'x', '/', 256 };
   const String& input = String::Handle(String::FromUTF16(kInput, kInputLen));
   const intptr_t kOutputLen = 10;
   const uint16_t kOutput[kOutputLen] =
       { 'x', '%', '2', 'F', '%', 'C', '4', '%', '8', '0' };
@@ skipping 3793 matching lines @@
   EXPECT_VALID(h_result);
   Integer& result = Integer::Handle();
   result ^= Api::UnwrapHandle(h_result);
   String& foo = String::Handle(String::New("foo"));
   Integer& expected = Integer::Handle();
   expected ^= foo.HashCode();
   EXPECT(result.IsIdenticalTo(expected));
 }
 
 }  // namespace dart