CVE-2022-23570: Null-dereference in Tensorflow

When decoding a tensor from protobuf, TensorFlow might do a null-dereference if attributes of some mutable arguments to some operations are missing from the proto. This is guarded by a DCHECK:

const auto* attr = attrs.Find(arg->s());
DCHECK(attr != nullptr);
if (attr->value_case() == AttrValue::kList) {
// ...
}

However, DCHECK is a no-op in production builds and an assertion failure in debug builds. In the first case execution proceeds to the dereferencing of the null pointer, whereas in the second case it results in a crash due to the assertion failure.