Fix null pointer dereference in handle_ipv4v6_addr
Fix null pointer dereference in handle_ipv4v6_addr

.. which was introduced in 2073b2 'Fix OFP_DEBUG compile-time define'

Clean up the RTM_XXXADDR messages too.

Signed-off-by: Brian Brooks <8e906ed46ccdc37d68771658f0f8f8740a374927@arm.com>
Reviewed-by: Bogdan Pricope <42ca93281c38a50e44216100dfc014dce41a2ed5@enea.com>

TolikH/ofp,TolikH/ofp,OpenFastPath/ofp,OpenFastPath/ofp,TolikH/ofp,OpenFastPath/ofp,OpenFastPath/ofp