message: [compiler] Fix segmentation faulit in segment graph
  Change the log message
diff: @@ -721,6 +721,10 @@ Status SegmentGraph(const Graph* tf_graph,
  std::vector<UnionFind<SimpleNode*>> node_segments;
  for (int i = 0; i < graph->num_node_ids(); ++i) {
  SimpleNode* node = graph->FindNodeId(i);
  + if (!node) {
  + VLOG(1) << "Node " << i << " doesn't exist in the graph";
  + continue;
  + }
  auto exclude_node = [&](absl::string_view reason) {
  VLOG(1) << "Not a TF-TRT candidate, "
  << "(Op type: " << node->tf_node()->type_string() << "), "
  