Fix crash in deferred_constraint_constants_test.

pkg/compiler/lib/src/compile_time_constants.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.
 
 library dart2js.compile_time_constant_evaluator;
 
 import 'constant_system_dart.dart';
 import 'constants/constant_system.dart';
 import 'constants/expressions.dart';
 import 'constants/values.dart';
@@ skipping 964 matching lines @@
     // and present some kind of stack-trace.
     compiler.reportError(node, message);
   }
 
   AstConstant signalNotCompileTimeConstant(Node node,
       {MessageKind message: MessageKind.NOT_A_COMPILE_TIME_CONSTANT}) {
     if (isEvaluatingConstant) {
       error(node, message);
 
       return new AstConstant(
-          null, node, new NullConstantExpression(new NullConstantValue()));
+          null, node, new ErroneousConstantExpression());
     }
     // Else we don't need to do anything. The final handler is only
     // optimistically trying to compile constants. So it is normal that we
     // sometimes see non-compile time constants.
     // Simply return [:null:] which is used to propagate a failing
     // compile-time compilation.
     return null;
   }
 }
 
@@ skipping 237 matching lines @@
   ErroneousAstConstant(Element element, Node node)
       : super(element, node, new ErroneousConstantExpression());
 }
 
 // TODO(johnniwinther): Avoid the need for this hack.
 TreeElements _analyzeElementEagerly(Compiler compiler, AstElement element) {
   WorldImpact worldImpact = compiler.analyzeElement(element.declaration);
   compiler.enqueuer.resolution.applyImpact(element.declaration, worldImpact);
   return element.resolvedAst.elements;
 }