message: Add a helper error message when the tensor index is not found.
diff: @@ -461,7 +461,7 @@ class SingleOpModel {
  std::vector<T> ExtractVector(int index) const {
  const T* v = interpreter_->typed_tensor<T>(index);
  const auto* tensor = interpreter_->tensor(index);
  - CHECK(v);
  + CHECK(v) << "Could not extract vector at index: " << index;
  int tensor_size;
  if (tensor->sparsity) {
  // Getting the size of the sparse buffer this way is based on the
  