message: Don't ignore sink == nullptr, let it crash instead.
diff: @@ -373,9 +373,8 @@ TFLogSinks& TFLogSinks::Instance() {
  }
  void TFLogSinks::Add(TFLogSink* sink) {
  - if(sink == nullptr) {
  - return;
  - }
  + assert(sink != nullptr && "The sink must not be a nullptr");
  +
  tensorflow::mutex_lock lock(mutex_);
  auto it = FindSink(sink);
  if(it == sinks_.end()) {
  @@ -384,9 +383,8 @@ void TFLogSinks::Add(TFLogSink* sink) {
  }
  void TFLogSinks::Remove(TFLogSink* sink) {
  - if(sink == nullptr) {
  - return;
  - }
  + assert(sink != nullptr && "The sink must not be a nullptr");
  +
  tensorflow::mutex_lock lock(mutex_);
  auto it = FindSink(sink);
  if(it != sinks_.end()) {
  