FIX: fixed a bug in correctAttenuationHB.
FIX: fixed a bug in correctAttenuationHB.

- the checks for attenuation overflow looked at the wrong gate
- the 'nan' and 'zero' mode assigned their values to the wrong gate

wradlib/wradlib,heistermann/wradlib,kmuehlbauer/wradlib,kmuehlbauer/wradlib,wradlib/wradlib,heistermann/wradlib