PVS-Studio warning V606 for VirtualBox

VBOXCMDVBVA_HDR* VBoxCmdVbvaSubmitLock(....)
{
  if (VBoxVBVAExGetSize(&pVbva->Vbva) < cbCmd)
  {
    WARN(("...."));
    NULL;                                        //<==
  }

  if (!VBoxVBVAExBufferBeginUpdate(....)
  {
    WARN(("VBoxVBVAExBufferBeginUpdate failed!"));
    return NULL;
  }
  ....
}

This suspicious code was found in VirtualBox project by PVS-Studio static code analyzer.
Warning message is:
V606 Ownerless token '0'. vboxmpvbva.cpp 997

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/