message: Handle model deserialization when output tensor shape is NULL.
  In flatbuffers, vectors default to NULL.
  Original change by alanchiao@.
diff: @@ -177,6 +177,11 @@ TfLiteStatus InterpreterBuilder::BuildLocalIndexToRegistrationMapping() {
  namespace {
  template <class T>
  std::vector<int> FlatBufferIntArrayToVector(T* flat_array) {
  + // Initialize shape of tensors with null shape. Empty vectors are converted
  + // to nullptr for models that are constructed via flatbuffers::Pack.
  + if (flat_array == nullptr) {
  + return {};
  + }
  std::vector<int> ret(flat_array->Length());
  for (int i = 0; i < flat_array->Length(); i++) {
  ret[i] = flat_array->Get(i);
  