message: Protection for empty friends
diff: @@ -715,10 +715,13 @@ void AliTPCcalibAlign::ExportTrackPoints(AliVEvent *event){
  AliTPCseed *seed0 = 0,*seed1=0;
  AliTPCseed tpcSeed0, tpcSeed1;
  //
  + Int_t nFriendTracks = Vfriend->GetNumberOfTracks();
  + if (index0 > nFriendTracks) continue; // most likely, we didn't save the friends for this event
  friendTrack = const_cast<AliVfriendTrack*>(Vfriend->GetTrack(index0));
  if (!friendTrack) continue;
  if (friendTrack->GetTPCseed(tpcSeed0)==0) seed0=&tpcSeed0;
  if (index1>0){
  + if (index1 > nFriendTracks) continue; // most likely, we didn't save the friends for this event
  friendTrack = const_cast<AliVfriendTrack*>(Vfriend->GetTrack(index1));
  if (!friendTrack) continue;
  if (friendTrack->GetTPCseed(tpcSeed1)==0) seed1=&tpcSeed1;
  