list delete: return if next element is null (fixes #20)
list delete: return if next element is null (fixes #20)

Signed-off-by: Alexander Dahl <9b466094ec991a03cb95c489c19c4d75635f0ae5@lespocky.de>

rafaelsteil/libcgi,LeSpocky/libcgi,rafaelsteil/libcgi,LeSpocky/libcgi