seg fault when error in proxy.conf

[Alan DeKok]

A.L.M.Buxey at lboro.ac.uk wrote:
> noted an issue with the reading of proxy.conf, if details
> are omitted from home_server section then it segfaults eg
...
> A quick check shows similar problem if secret or port is absent but
> not sure where else the parser breaks with a similar fault.

  Looking at the conf file parser, it's not doing enough checking for
NULL pointers.  I've committed a fix.

  Alan DeKok.