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runtime/bin/vmservice/client/lib/src/service/service.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.
 
 part of service;
 
 /// A [ServiceObject] is an object known to the VM service and is tied
 /// to an owning [Isolate].
 abstract class ServiceObject extends Observable {
   Isolate _isolate;
@@ skipping 146 matching lines @@
     } else if (v is ObservableMap) {
       _upgradeObservableMap(v, vm, isolate);
     }
   }
 }
 
 /// Upgrades response ([m]) from [vm] and [isolate] to a [ServiceObject].
 /// This acts like a factory which consumes an ObservableMap and returns
 /// a fully upgraded ServiceObject.
 ServiceObject _upgradeToServiceObject(VM vm, Isolate isolate, ObservableMap m) {
+  if (m == null) {
+    return null;
+  }
   if (!ServiceObject.isServiceMap(m)) {
     Logger.root.severe("Malformed service object: $m");
   }
   assert(ServiceObject.isServiceMap(m));
   var type = ServiceObject.stripRef(m['type']);
   switch (type) {
     case 'Error':
       return new ServiceError.fromMap(isolate, m);
     case 'IsolateList':
       vm.isolates.update(m);
       return vm.isolates;
     case 'Script':
       return isolate.scripts.putIfAbsent(m);
     case 'Code':
       return isolate.codes.putIfAbsent(m);
     case 'Isolate':
       return vm.isolates.getIsolateFromMap(m);
     case 'Class':
       return isolate.classes.putIfAbsent(m);
     case 'Function':
       return isolate.functions.putIfAbsent(m);
   }
   return new ServiceMap.fromMap(isolate, m);
 }