message: [SE] Don't CHECK-fail when the stream is not-OK
  This check-fail was wrong anyway; it meant to check the *substream's* status, but checked its own anyway. We could be in an error state and that's absolutely fine, we shouldn't kill the process for this.
diff: @@ -1959,7 +1959,9 @@ Stream *Stream::GetOrCreateSubStream() {
  false);
  Stream *sub_stream = sub_streams_.back().first.get();
  sub_stream->Init();
  - CHECK(ok_) << "sub-stream failed to be initialized";
  + if (!sub_stream->ok_) {
  + LOG(ERROR) << "sub-stream failed to be initialized";
  + }
  VLOG(1) << DebugStreamPointers() << " created new sub_stream "
  << sub_stream->DebugStreamPointers();
  