message: Prevent a null-pointer dereference / `CHECK`-fail in grappler.
diff: @@ -75,8 +75,10 @@ bool DependencyOptimizer::SafeToRemoveIdentity(const NodeDef& node) const {
  }
  const NodeDef* input = node_map_->GetNode(NodeName(node.input(0)));
  - CHECK(input != nullptr) << "node = " << node.name()
  - << " input = " << node.input(0);
  + if (input == nullptr) {
  + VLOG(1) << "node = " << node.name() << " input = " << node.input(0);
  + return false;
  + }
  // Don't remove Identity nodes corresponding to Variable reads or following
  // Recv.
  if (IsVariable(*input) || IsRecv(*input)) {
  