Don't crash on static/non-static acccessors.

pkg/front_end/lib/src/fasta/kernel/builder_accessors.dart

 // Copyright (c) 2016, 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 fasta.builder_accessors;
 
 export 'frontend_accessors.dart' show wrapInvalid;
 
 import 'frontend_accessors.dart' show Accessor;
 
@@ skipping 417 matching lines @@
     if (receiver is KernelClassBuilder) {
       Builder builder = receiver.findStaticBuilder(name.name, charOffset, uri);
       Member getter = builder?.target;
       Member setter;
       if (builder == null) {
         builder = receiver.findStaticBuilder(name.name, charOffset, uri,
             isSetter: true);
         if (builder == null) {
           return buildThrowNoSuchMethodError(null);
         }
+        setter = builder.target;
       }
       if (builder.hasProblem) {
         return helper.buildProblemExpression(builder, name.name)
           ..fileOffset = charOffset;
       }
       if (getter is Field) {
         if (!getter.isFinal && !getter.isConst) {
           setter = getter;
         }
       } else if (getter is Procedure) {
         if (getter.isGetter) {
           builder = receiver.findStaticBuilder(name.name, charOffset, uri,
               isSetter: true);
           if (builder != null && !builder.hasProblem) {
             setter = builder.target;
           }
         }
       }
-      if (getter == null) {
-        return internalError("no getter for $name");
+      if (getter == null && setter == null) {
+        return internalError("No accessor for '$name'.");
       }
       return new StaticAccessor(helper, charOffset, getter, setter);
     }
     return PropertyAccessor.make(helper, charOffset, helper.toValue(receiver),
         name, null, null, isNullAware);
   }
 
   Expression buildNullAwareAssignment(Expression value, DartType type,
       {bool voidContext: false}) {
     return internalError("Unhandled");
@@ skipping 287 matching lines @@
             buildIsNull(new VariableGet(variable)),
             new NullLiteral(),
             new MethodInvocation(new VariableGet(variable), name, arguments)
               ..fileOffset = charOffset,
             const DynamicType()));
   } else {
     return new MethodInvocation(receiver, name, arguments)
       ..fileOffset = charOffset;
   }
 }