Check for null constructor field initializer expression.

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

Index: pkg/analyzer/lib/src/dart/constant/evaluation.dart
diff --git a/pkg/analyzer/lib/src/dart/constant/evaluation.dart b/pkg/analyzer/lib/src/dart/constant/evaluation.dart
index 9dc5c7e510c182f0aeba1ce28f2417a1d2bb7e39..fc3ee08a412129963d06152b5ec9e98c641ff8a3 100644
--- a/pkg/analyzer/lib/src/dart/constant/evaluation.dart
+++ b/pkg/analyzer/lib/src/dart/constant/evaluation.dart
@@ -709,7 +709,7 @@ class ConstantEvaluationEngine {
       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)) {
@@ -728,6 +728,9 @@ class ConstantEvaluationEngine {
                   [evaluationResult.type, fieldName, field.type]);
             }
           }
+        } else {
+          errorReporter.reportErrorForNode(
+              CompileTimeErrorCode.CONST_EVAL_THROWS_EXCEPTION, node);
         }
       } else if (initializer is SuperConstructorInvocation) {
         SimpleIdentifier name = initializer.constructorName;