Logstash filebeat error

Logstash filebeat error

    {:timestamp=>"2016-10-28T17:21:44.445000+0100", :message=>"Pipeline aborted due to error", :exception=>java.lang.NullPointerException, :backtrace=>["org.logstash.netty.PrivateKeyConverter.generatePkcs8(org/logstash/netty/PrivateKeyConverter.java:43)", "org.logstash.netty.PrivateKeyConverter.convert(org/logstash/netty/PrivateKeyConverter.java:39)", "java.lang.reflect.Method.invoke(java/lang/reflect/Method.java:498)", "RUBY.create_server(/usr/share/logstash/vendor/bundle/jruby/1.9/gems/logstash-input-beats-3.1.0.beta4-java/lib/logstash/inputs/beats.rb:139)", "RUBY.register(/usr/share/logstash/vendor/bundle/jruby/1.9/gems/logstash-input-beats-3.1.0.beta4-java/lib/logstash/inputs/beats.rb:132)", "RUBY.start_inputs(/usr/share/logstash/logstash-core/lib/logstash/pipeline.rb:311)", "org.jruby.RubyArray.each(org/jruby/RubyArray.java:1613)", "RUBY.start_inputs(/usr/share/logstash/logstash-core/lib/logstash/pipeline.rb:310)", "RUBY.start_workers(/usr/share/logstash/logstash-core/lib/logstash/pipeline.rb:187)", "RUBY.run(/usr/share/logstash/logstash-core/lib/logstash/pipeline.rb:145)", "RUBY.start_pipeline(/usr/share/logstash/logstash-core/lib/logstash/agent.rb:240)", "java.lang.Thread.run(java/lang/Thread.java:745)"], :level=>:error}
    {:timestamp=>"2016-10-28T17:21:47.452000+0100", :message=>"stopping pipeline", :id=>"main", :level=>:warn}
    {:timestamp=>"2016-10-28T17:21:47.456000+0100", :message=>"An unexpected error occurred!", :error=>#<NoMethodError: undefined method `stop' for nil:NilClass>, :backtrace=>["/usr/share/logstash/vendor/bundle/jruby/1.9/gems/logstash-input-beats-3.1.0.beta4-java/lib/logstash/inputs/beats.rb:173:in `stop'", "/usr/share/logstash/logstash-core/lib/logstash/inputs/base.rb:88:in `do_stop'", "org/jruby/RubyArray.java:1613:in `each'", "/usr/share/logstash/logstash-core/lib/logstash/pipeline.rb:366:in `shutdown'", "/usr/share/logstash/logstash-core/lib/logstash/agent.rb:252:in `stop_pipeline'", "/usr/share/logstash/logstash-core/lib/logstash/agent.rb:261:in `shutdown_pipelines'", "org/jruby/RubyHash.java:1342:in `each'", "/usr/share/logstash/logstash-core/lib/logstash/agent.rb:261:in `shutdown_pipelines'", "/usr/share/logstash/logstash-core/lib/logstash/agent.rb:123:in `shutdown'", "/usr/share/logstash/logstash-core/lib/logstash/runner.rb:237:in `execute'", "/usr/share/logstash/vendor/bundle/jruby/1.9/gems/clamp-0.6.5/lib/clamp/command.rb:67:in `run'", "/usr/share/logstash/logstash-core/lib/logstash/runner.rb:157:in `run'", "/usr/share/logstash/vendor/bundle/jruby/1.9/gems/clamp-0.6.5/lib/clamp/command.rb:132:in `run'", "/usr/share/logstash/lib/bootstrap/environment.rb:66:in `(root)'"], :level=>:fatal}