Logstashのoutputをsyslogに設定時にエラー

logstashにて、outputをsyslogにした際に以下のエラーが発生しました。
原因についてご教示頂けないでしょうか

■confファイル内容

input {
    file{
        path => "/XXX/test.log"
        start_position => "beginning"
    }
}
output{
    syslog{
        host => "XXXXXX.com"
        port => 6514
        protocol => "ssl-tcp"
    }
}

■エラー内容
2020-03-18T18:56:12,703][ERROR][logstash.agent ] Failed to execute action {:id=>:ddi_threat, :action_type=>LogStash::ConvergeResult::FailedAction, :message=>"Could not execute action: PipelineAction::Create<ddi_threat>, action_result: false", :backtrace=>nil}
[2020-03-18T18:56:15,699][ERROR][logstash.javapipeline ][ddi_threat] Pipeline aborted due to error {:pipeline_id=>"ddi_threat", :exception=>#<TypeError: no implicit conversion of nil into String>, :backtrace=>["org/jruby/RubyIO.java:3778:in read'", "/usr/share/logstash/vendor/bundle/jruby/2.5.0/gems/logstash-output-syslog-3.0.5/lib/logstash/outputs/syslog.rb:229:in setup_ssl'", "/usr/share/logstash/vendor/bundle/jruby/2.5.0/gems/logstash-output-syslog-3.0.5/lib/logstash/outputs/syslog.rb:132:in register'", "org/logstash/config/ir/compiler/OutputStrategyExt.java:106:in register'", "org/logstash/config/ir/compiler/AbstractOutputDelegatorExt.java:48:in register'", "/usr/share/logstash/logstash-core/lib/logstash/java_pipeline.rb:200:in block in register_plugins'", "org/jruby/RubyArray.java:1814:in each'", "/usr/share/logstash/logstash-core/lib/logstash/java_pipeline.rb:199:in register_plugins'", "/usr/share/logstash/logstash-core/lib/logstash/java_pipeline.rb:501:in maybe_setup_out_plugins'", "/usr/share/logstash/logstash-core/lib/logstash/java_pipeline.rb:212:in start_workers'", "/usr/share/logstash/logstash-core/lib/logstash/java_pipeline.rb:154:in run'", "/usr/share/logstash/logstash-core/lib/logstash/java_pipeline.rb:109:in block in start'"], "pipeline.sources"=>["/etc/logstash/conf.d/lab001/lab001_ddi_threat.conf"], :thread=>"#<Thread:0x62f22fc9 run>"}
[2020-03-18T18:56:15,713][ERROR][logstash.agent ] Failed to execute action {:id=>:ddi_threat, :action_type=>LogStash::ConvergeResult::FailedAction, :message=>"Could not execute action: PipelineAction::Create<ddi_threat>, action_result: false", :backtrace=>nil}
[2020-03-18T18:56:18,686][ERROR][logstash.javapipeline ][ddi_threat] Pipeline aborted due to error {:pipeline_id=>"ddi_threat", :exception=>#<TypeError: no implicit conversion of nil into String>, :backtrace=>["org/jruby/RubyIO.java:3778:in read'", "/usr/share/logstash/vendor/bundle/jruby/2.5.0/gems/logstash-output-syslog-3.0.5/lib/logstash/outputs/syslog.rb:229:in setup_ssl'", "/usr/share/logstash/vendor/bundle/jruby/2.5.0/gems/logstash-output-syslog-3.0.5/lib/logstash/outputs/syslog.rb:132:in register'", "org/logstash/config/ir/compiler/OutputStrategyExt.java:106:in register'", "org/logstash/config/ir/compiler/AbstractOutputDelegatorExt.java:48:in register'", "/usr/share/logstash/logstash-core/lib/logstash/java_pipeline.rb:200:in block in register_plugins'", "org/jruby/RubyArray.java:1814:in each'", "/usr/share/logstash/logstash-core/lib/logstash/java_pipeline.rb:199:in register_plugins'", "/usr/share/logstash/logstash-core/lib/logstash/java_pipeline.rb:501:in maybe_setup_out_plugins'", "/usr/share/logstash/logstash-core/lib/logstash/java_pipeline.rb:212:in start_workers'", "/usr/share/logstash/logstash-core/lib/logstash/java_pipeline.rb:154:in run'", "/usr/share/logstash/logstash-core/lib/logstash/java_pipeline.rb:109:in block in start'"], "pipeline.sources"=>["/etc/logstash/conf.d/lab001/lab001_ddi_threat.conf"], :thread=>"#<Thread:0x15890e5e run>"}