Check for null constructor field initializer expression.

pkg/analyzer/lib/src/dart/constant/evaluation.dart

 // Copyright (c) 2014, 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 analyzer.src.dart.constant.evaluation;
 
 import 'dart:collection';
 
 import 'package:analyzer/context/declared_variables.dart';
 import 'package:analyzer/dart/ast/ast.dart';
@@ skipping 691 matching lines @@
     }
     ConstantVisitor initializerVisitor = new ConstantVisitor(
         this, externalErrorReporter,
         lexicalEnvironment: parameterMap);
     String superName = null;
     NodeList<Expression> superArguments = null;
     for (ConstructorInitializer initializer in initializers) {
       if (initializer is ConstructorFieldInitializer) {
         Expression initializerExpression = initializer.expression;
         DartObjectImpl evaluationResult =
-            initializerExpression.accept(initializerVisitor);
+            initializerExpression?.accept(initializerVisitor);
         if (evaluationResult != null) {
           String fieldName = initializer.fieldName.name;
           if (fieldMap.containsKey(fieldName)) {
             errorReporter.reportErrorForNode(
                 CompileTimeErrorCode.CONST_EVAL_THROWS_EXCEPTION, node);
           }
           fieldMap[fieldName] = evaluationResult;
           PropertyAccessorElement getter = definingClass.getGetter(fieldName);
           if (getter != null) {
             PropertyInducingElement field = getter.variable;
             if (!runtimeTypeMatch(evaluationResult, field.type)) {
               errorReporter.reportErrorForNode(
                   CheckedModeCompileTimeErrorCode
                       .CONST_CONSTRUCTOR_FIELD_TYPE_MISMATCH,
                   node,
                   [evaluationResult.type, fieldName, field.type]);
             }
           }
+        } else {
+          errorReporter.reportErrorForNode(
+              CompileTimeErrorCode.CONST_EVAL_THROWS_EXCEPTION, node);
         }
       } else if (initializer is SuperConstructorInvocation) {
         SimpleIdentifier name = initializer.constructorName;
         if (name != null) {
           superName = name.name;
         }
         superArguments = initializer.argumentList.arguments;
       } else if (initializer is RedirectingConstructorInvocation) {
         // This is a redirecting constructor, so just evaluate the constructor
         // it redirects to.
@@ skipping 1389 matching lines @@
   }
 
   @override
   String toString() {
     if (value == null) {
       return "error";
     }
     return value.toString();
   }
 }