message: mccollisionlabel only filled when collision has been stored
diff: @@ -2464,10 +2464,12 @@ void AliAnalysisTaskAO2Dconverter::FillEventInTF()
  FillTree(kMcCollision);
  // MC collision label
  + // will be joined with Collisions, therefore fill it only when we fill Collisions
  + if (fillCollision) {
  mccollisionlabel.fIndexMcCollisions = fBCCount;
  mccollisionlabel.fMcMask = 0;
  FillTree(kMcCollisionLabel);
  -
  + }
  //---------------------------------------------------------------------------
  // Update the offsets at the end of each collision
  