Don't assume ICONV_NULL = 0
Don't assume ICONV_NULL = 0

We define the value ICONV_NULL = -1, but when we attempt to set the
s_iconv_convs array to all NULL values, we zero the array instead of setting
its entries to -1.

This patch properly initializes and wipes s_iconv_convs.

Arkq/fluxbox,olivergondza/fluxbox,Arkq/fluxbox,Arkq/fluxbox,luebking/fluxbox,olivergondza/fluxbox,naimdjon/fluxbox,lukoko/fluxbox,Arkq/fluxbox,olivergondza/fluxbox,Arkq/fluxbox,lukoko/fluxbox,luebking/fluxbox,luebking/fluxbox,naimdjon/fluxbox,lukoko/fluxbox,naimdjon/fluxbox,luebking/fluxbox,lukoko/fluxbox,naimdjon/fluxbox,luebking/fluxbox,olivergondza/fluxbox,naimdjon/fluxbox,lukoko/fluxbox,olivergondza/fluxbox