message: Fix undefined behavior in VectorImpl
  Summary: memcpy on null operands is undefined, add a test.
diff: @@ -124,6 +124,9 @@ ssize_t VectorImpl::insertArrayAt(const void* array, size_t index, size_t length
  {
  if (index > size())
  return BAD_INDEX;
  + if (!length) {
  + return index;
  + }
  void* where = _grow(index, length);
  if (where) {
  _do_copy(where, array, length);
  @@ -640,4 +643,3 @@ ssize_t SortedVectorImpl::remove(const void* item)
  /*****************************************************************************/
  }; // namespace android
  -
  