If the read values are Nan set them to 0 (SP w/ cav)

This could happen when during the calibration the W is negative.

src/sis8300llrfSPWithCavityChannel.cpp

@@ -80,6 +80,8 @@ ndsStatus sis8300llrfSPWithCavityChannel::updateMagAngRBV() {
     // if gradient calibration is enabled
     if (m_CavChannel->isGradCalibrated()) {
         _MagRBV = m_CavChannel->calibrateGrad(calibratorRaw2EGU->calibrate(_MagRaw));
+       if (_MagRBV != _MagRBV) // Nan
+           _MagRBV = 0;
     }
     else
         if (calibratorRaw2EGU->isEnabled())
@@ -226,6 +228,8 @@ ndsStatus sis8300llrfSPWithCavityChannel::getMagTable(
     if (m_CavChannel->isGradCalibrated()) {
        for (int i = 0; i <  _MagTableCount; i++){
            value[i] = m_CavChannel->calibrateGrad(calibratorRaw2EGU->calibrate(_MagTable[i]));
+           if (value[i] != value[i]) // Nan
+               value[i] = 0;
         }
     }
     else