message: Protection agains Distortion RMS paramet. < 0
diff: @@ -186,6 +186,7 @@ inline void AliTPCChebCorr::Eval(int sector, int row, float y2x, float z, float
  float tz[2] = {y2x,z}; // params use row, Y/X, Z
  const AliCheb2DStack* par = GetParam(sector,y2x,z);
  if (par) par->Eval(row, tz, corr);
  + if (corr[3]<0) corr[3] = 10e-4;
  //
  }
  @@ -197,6 +198,7 @@ inline void AliTPCChebCorr::Eval(int sector, int row, float tz[2], float *corr)
  if (sector>kMaxIROCSector) row += kNRowsIROC; // we are in OROC
  const AliCheb2DStack* par = GetParam(sector,tz[0],tz[1]);
  if (par) par->Eval(row, tz, corr);
  + if (corr[3]<0) corr[3] = 10e-4;
  //
  }
  @@ -208,7 +210,8 @@ inline Float_t AliTPCChebCorr::Eval(int sector, int row, float y2x, float z, int
  if (sector>kMaxIROCSector) row += kNRowsIROC; // we are in OROC
  float tz[2] = {y2x,z}; // params use row, Y/X, Z
  const AliCheb2DStack* par = GetParam(sector,y2x,z);
  - return par ? par->Eval(row, dimOut, tz) : 0;
  + float res = par ? par->Eval(row, dimOut, tz) : 0;
  + return res<0. ? (dimOut==3 ? 10.e-4 : res) : res;
  //
  }
  @@ -219,7 +222,8 @@ inline Float_t AliTPCChebCorr::Eval(int sector, int row, float tz[2], int dimOut
  // Sector is in 0-71 ROC convention, to check Zs outlying from the sector
  if (sector>kMaxIROCSector) row += kNRowsIROC; // we are in OROC
  const AliCheb2DStack* par = GetParam(sector,tz[0],tz[1]);
  - return par ? par->Eval(row, dimOut, tz) : 0;
  + float res = par ? par->Eval(row, dimOut, tz) : 0;
  + return res<0. ? (dimOut==3 ? 10.e-4 : res) : res;
  //
  }
  