operate_do: skip superfluous check for NULL pointer

Coverity CID 1243583. get_url_file_name() cannot fail and return a NULL
file name pointer so skip the check for that - it tricks coverity into
believing it can happen and it then warns later on when we use 'outfile'
without checking for NULL.
krb5_encode: remove unused argument

Coverity CID 1241957. Removed the unused argument. As this struct and
pointer now are used only for krb5, there's no need to keep unused
function arguments around.
do_sec_send: remove dead code

Coverity CID 1241951. The condition 'len >= 0' would always be true at
that point and thus not necessary to check for.
operate: avoid NULL dereference

Coverity CID 1241948. dumpeasysrc() would get called with
config->current set to NULL which could be dereferenced by a warnf()
call.