Fix debugger

tool/input_sdk/private/ddc_runtime/rtti.dart

 // Copyright (c) 2015, 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.
 
 /// This library defines the association between runtime objects and
 /// runtime types.
 part of dart._runtime;
 
 /// Runtime type information.  This module defines the mapping from
 /// runtime objects to their runtime type information.  See the types
@@ skipping 120 matching lines @@
   result = getExtensionType(obj);
   if (result != null) return result;
 
   // Fallback on constructor for class types
   result = JS('', '#.constructor', obj);
   if (JS('bool', '# === Function', result)) {
     // An undecorated Function should have come from JavaScript.
     // Treat as untyped.
     return JS('', '#', jsobject);
   }
+  if (result == null) {
+    return JS('', '#', jsobject);
+  }
   return result;
 }
 
 /// Given an internal runtime type object, wraps it in a `WrappedType` object
 /// that implements the dart:core Type interface.
 wrapType(type) {
   // If we've already wrapped this type once, use the previous wrapper. This
   // way, multiple references to the same type return an identical Type.
   if (JS('bool', '#.hasOwnProperty(#)', type, _typeObject)) {
     return JS('', '#[#]', type, _typeObject);
@@ skipping 12 matching lines @@
 }
 
 void tagComputed(value, compute) {
   JS('', '#(#, #, { get: # })', defineProperty, value, _runtimeType, compute);
 }
 
 void tagLazy(value, compute) {
   JS('', '#(#, #, { get: # })',
       defineLazyProperty, value, _runtimeType, compute);
 }