fix mixin config_name in the name.nil? case
fix mixin config_name in the name.nil? case

opentable/logstash-kafka,tinglinux/logstash-kafka,Aloomaio/logstash-kafka,Aloomaio/logstash-kafka,joekiller/logstash-kafka,opentable/logstash-kafka,tinglinux/logstash-kafka,joekiller/logstash-kafka