netfilter: nf_log: Remove NULL check

If 'logger' was NULL, there would be a direct jump to the label 'out',
since it has already been checked for NULL, remove this unnecessary
check.

Signed-off-by: Shivani Bhardwaj <shivanib134@gmail.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>