message: Work around TGeoHMatrix bug in ROOT v6-14-04
  `operator=()` does not work properly any longer if a null pointer is passed as
  value. The intended behaviour is to invoke `Clear()` to the given instance of
  `TGeoHMatrix`. This fix in AliRoot makes it work as intended without waiting for
  a fix in ROOT.
diff: @@ -554,7 +554,7 @@ void AliTOFtracker::MatchTracks( Int_t mLastStep){
  fTOFtrackPoints->Delete();
  for (Int_t ii=0; ii<kNclusterMax; ii++)
  - global[ii] = 0x0;
  + global[ii].Clear();
  AliTOFtrack *track =(AliTOFtrack*)fTracks->UncheckedAt(iseed);
  AliESDtrack *t =(AliESDtrack*)fSeeds->At(track->GetSeedIndex());
  //if ( t->GetTOFsignal()>0. ) continue;
  