RS41 Humidity calculation

[srcejon]

In RX_FSK/src/RS41.cpp, there's code based on https://github.com/einergehtnochrein/ra-firmware

Around line 648 the code is:

   float Tp = (sensorTemp - 20.0f) / 180.0f;
   float sum = 0;
   float powc = 1.0f;
   float p = pressure / 1000.0f;
   for ( int i = 0; i < 3; i++) {
      float l = 0;
      float powt = 1.0f;
      for ( int j = 0; j < 4; j++) {
         l += calibration->value.matrixBt[4*i+j] * powt;
         powt *= Tp;
      }
      float x = calibration->value.vectorBp[i];
      sum += l * (x * p / (1.0f + x * p) - x * powc / (1.0f + x));
      powc *= Cp;
   }
   Cp -= sum;

   // Should sum be set to 0 here?

   float xj = 1.0f;
   for ( int j = 0; j < 7; j++) {
      float yk = 1.0f;
      for ( int k = 0; k < 6; k++) {
         sum += xj * yk * calibration->value.matrixU[j][k];
         yk *= Tp;
      }
      xj *= Cp;
   } 

   float RH = sum

However, in the original version of the code https://github.com/einergehtnochrein/ra-firmware/blob/master/src/rs41/rs41metrology.c at line 271, sum is set to 0 between the two loops, but that seems to be missing here.