PVS-Studio warning V522 for ffdshow

STDMETHODIMP_(bool) TffdshowDecAudioInputPin::getsf(
  TsampleFormat &outsf)
{
  if (!audio)                                      <<<---
  {
    .... // audio don't used
    } else if (bitstream_codec(audio->codecId)) {  <<<---
      outsf.sf = TsampleFormat::getSampleFormat(codecId);
      outsf.alternateSF = filter->insf.alternateSF;
      return true;
    }
  } else {
  .....
}

This suspicious code was found in ffdshow project by PVS-Studio static code analyzer.
Warning message is:
V522 Dereferencing of the null pointer 'audio' might take place. tffdshowdecaudioinputpin.cpp 468

PVS-Studio is a static analyzer for detecting bugs in the source code of applications written in C, C++, C++11, C++/CX. Site: http://www.viva64.com/en/pvs-studio/