PVS-Studio warning V595 for Pthreads

int
pthread_key_delete (pthread_key_t key)
{
  ...
  while ((assoc = (ThreadKeyAssoc *) key->threads) != NULL)
  {
     ptw32_thread_t * thread = assoc->thread;
     if (assoc == NULL)
     {
       /* Finished */
       break;
     }
     ...
  }
  ...
}

This suspicious code was found in Pthreads project by PVS-Studio static code analyzer.
Warning message is:
V595 The 'assoc' pointer was utilized before it was verified against nullptr. Check lines: 88, 90. pthread80 pthread_key_delete.c 88

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