message: fix for variable name of cov matrix
diff: @@ -308,9 +308,11 @@ const char * AliNanoAODTrackMapping::GetVarName(Int_t index) const {
  else if(index == fTRDnSlices ) return "TRDnSlices" ;
  for (Int_t i=0; i<21; i++) {
  -
  - if(index == fcovmat[i]) return TString::Format("covmat%d",i).Data();
  -
  + if(index == fcovmat[i]) {
  + static TString retValue;
  + retValue = TString::Format("covmat%d",i);
  + return retValue;
  + }
  }
  if (index >= fSize) {
  AliWarning(Form("Invalid index %d", index));
  