Possible divide by 0 in aggregate.cpp

This line could result in a divide by 0 error.

aggregated[dataIndex] *=
    OEL_PI * geoData.auCorrection /
    (solIrrL1a[l1bBand] * cosSolZens[currScan * geoData.numCcdPix + pix]);

This should be guarded against even if it's unlikely.