message: Fix an unitialised variable warning and unused variable.
  Summary: Resolves Resolves T50879
  Reviewers: #tensorflow, #framework_ip_review_-_any_oss_or_third-party_code_use_has_been_approved, georgep
  Maniphest Tasks: T50879
diff: @@ -742,8 +742,6 @@ absl::optional<Tilesets> PartitionTiles(const poplar::Graph& main_graph,
  CHECK_LT(num_io_tiles, num_tiles_per_ipu);
  - const auto num_compute_tiles = num_tiles_per_ipu - num_io_tiles;
  -
  const auto io_tiles = gcl::perIPUTiles(main_graph, 0, num_io_tiles,
  /*sorted=*/true, /*tilePairs=*/true);
  CHECK_EQ(io_tiles.size(), num_io_tiles);
  @@ -1699,7 +1697,7 @@ StatusOr<std::unique_ptr<PoplarExecutableCore>> CompileEngine(
  std::unique_ptr<poplar::Engine> engine;
  std::vector<poplar::program::Program> progs;
  - bool logging_cycle_count;
  + bool logging_cycle_count = false;
  if (compile) {
  Tracepoint tracepoint("ExecutableConstruction");
  