PVS-Studio warning V522 for VTK

VTK_THREAD_RETURN_TYPE vtkTestCondVarThread( void* arg )
{
  ...
  if ( td )                  <<<---
  {
    ...
  }
  else
  {
    cout << "No thread data!\n";
    cout << "  Thread " << ( threadId + 1 )
         << " of " << threadCount << " exiting.\n";

    -- td->NumberOfWorkers;  <<<---

    cout.flush();
  }
  ...
}

This suspicious code was found in VTK project by PVS-Studio static code analyzer.
Warning message is:
V522 Dereferencing of the null pointer 'td' might take place. CommonCxxTests testconditionvariable.cxx 96

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/