[FATAL][logstash.runner ] An unexpected error occurred!

[FATAL][logstash.runner ] An unexpected error occurred! {:error=>#<TypeError: can't convert nil into String>, :backtrace=>["org/jruby/RubyArray.java:1892:in `join'", "org/jruby/RubyArray.java:1898:in `join'", "/usr/local/logstash/logstash-core/lib/logstash/util/buftok.rb:87:in `extract'", "/usr/local/logstash/vendor/bundle/jruby/1.9/gems/logstash-codec-json_lines-3.0.2/lib/logstash/codecs/json_lines.rb:40:in `decode'", "/usr/local/logstash/vendor/bundle/jruby/1.9/gems/logstash-input-kafka-5.1.0/lib/logstash/inputs/kafka.rb:237:in `thread_runner'", "file:/usr/local/logstash/vendor/jruby/lib/jruby.jar!/jruby/java/java_ext/java.lang.rb:12:in `each'", "/usr/local/logstash/vendor/bundle/jruby/1.9/gems/logstash-input-kafka-5.1.0/lib/logstash/inputs/kafka.rb:236:in `thread_runner'"]}