Make sure Bigint._digits is always a Uint32List (instead of sometimes null).

runtime/vm/object.h

 // Copyright (c) 2012, 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.
 
 #ifndef VM_OBJECT_H_
 #define VM_OBJECT_H_
 
 #include "include/dart_api.h"
 #include "platform/assert.h"
 #include "platform/utils.h"
@@ skipping 6722 matching lines @@
       }
     }
   }
 
   static bool IsTypedData(const Instance& obj) {
     ASSERT(!obj.IsNull());
     intptr_t cid = obj.raw()->GetClassId();
     return RawObject::IsTypedDataClassId(cid);
   }
 
+  static RawTypedData* EmptyUint32Array(Isolate* isolate);
+
  protected:
   void SetLength(intptr_t value) const {
     raw_ptr()->length_ = Smi::New(value);
   }
 
  private:
   static const intptr_t element_size[];
 
   FINAL_HEAP_OBJECT_IMPLEMENTATION(TypedData, Instance);
   friend class Class;
@@ skipping 723 matching lines @@
 
 
 RawObject* MegamorphicCache::GetTargetFunction(const Array& array,
                                                intptr_t index) {
   return array.At((index * kEntryLength) + kTargetFunctionIndex);
 }
 
 }  // namespace dart
 
 #endif  // VM_OBJECT_H_