logstash gelf exception

gistfile1.txt

{:timestamp=>"2013-08-22T14:34:33.770000-0500", :message=>"Output thread exception", :plugin=><LogStash::Outputs::Gelf facility=>"%{syslog_facility}", level=>["%{syslog_severity}"], host=>"127.0.0.1", sender=>"%{@source_host}", file=>"%{@source_path}", ignore_metadata=>["severity", "source_host", "source_path", "short_message"], full_message=>"%{@message}", short_message=>"short_message">, :exception=>#<NoMethodError: undefined method `downcase' for nil:NilClass>, :backtrace=>["file:/usr/local/logging/logstash-1.1.13/logstash-1.1.13-monolithic.jar!/logstash/outputs/gelf.rb:193:in `receive'", "file:/usr/local/logging/logstash-1.1.13/logstash-1.1.13-monolithic.jar!/logstash/outputs/base.rb:55:in `handle'", "file:/usr/local/logging/logstash-1.1.13/logstash-1.1.13-monolithic.jar!/logstash/agent.rb:805:in `run_output'", "file:/usr/local/logging/logstash-1.1.13/logstash-1.1.13-monolithic.jar!/logstash/agent.rb:419:in `start_output'"], :level=>:warn}
rate: 137.1745003240963
{:timestamp=>"2013-08-22T14:34:38.770000-0500", :message=>"Output thread exception", :plugin=><LogStash::Outputs::Gelf facility=>"%{syslog_facility}", level=>["%{syslog_severity}"], host=>"127.0.0.1", sender=>"%{@source_host}", file=>"%{@source_path}", ignore_metadata=>["severity", "source_host", "source_path", "short_message"], full_message=>"%{@message}", short_message=>"short_message">, :exception=>#<NoMethodError: undefined method `downcase' for nil:NilClass>, :backtrace=>["file:/usr/local/logging/logstash-1.1.13/logstash-1.1.13-monolithic.jar!/logstash/outputs/gelf.rb:193:in `receive'", "file:/usr/local/logging/logstash-1.1.13/logstash-1.1.13-monolithic.jar!/logstash/outputs/base.rb:55:in `handle'", "file:/usr/local/logging/logstash-1.1.13/logstash-1.1.13-monolithic.jar!/logstash/agent.rb:805:in `run_output'", "file:/usr/local/logging/logstash-1.1.13/logstash-1.1.13-monolithic.jar!/logstash/agent.rb:419:in `start_output'"], :level=>:warn}
rate: 126.2066328527531
{:timestamp=>"2013-08-22T14:34:43.770000-0500", :message=>"Output thread exception", :plugin=><LogStash::Outputs::Gelf facility=>"%{syslog_facility}", level=>["%{syslog_severity}"], host=>"127.0.0.1", sender=>"%{@source_host}", file=>"%{@source_path}", ignore_metadata=>["severity", "source_host", "source_path", "short_message"], full_message=>"%{@message}", short_message=>"short_message">, :exception=>#<NoMethodError: undefined method `downcase' for nil:NilClass>, :backtrace=>["file:/usr/local/logging/logstash-1.1.13/logstash-1.1.13-monolithic.jar!/logstash/outputs/gelf.rb:193:in `receive'", "file:/usr/local/logging/logstash-1.1.13/logstash-1.1.13-monolithic.jar!/logstash/outputs/base.rb:55:in `handle'", "file:/usr/local/logging/logstash-1.1.13/logstash-1.1.13-monolithic.jar!/logstash/agent.rb:805:in `run_output'", "file:/usr/local/logging/logstash-1.1.13/logstash-1.1.13-monolithic.jar!/logstash/agent.rb:419:in `start_output'"], :level=>:warn}
rate: 126.2066328527531
{:timestamp=>"2013-08-22T14:34:48.770000-0500", :message=>"Output thread exception", :plugin=><LogStash::Outputs::Gelf facility=>"%{syslog_facility}", level=>["%{syslog_severity}"], host=>"127.0.0.1", sender=>"%{@source_host}", file=>"%{@source_path}", ignore_metadata=>["severity", "source_host", "source_path", "short_message"], full_message=>"%{@message}", short_message=>"short_message">, :exception=>#<NoMethodError: undefined method `downcase' for nil:NilClass>, :backtrace=>["file:/usr/local/logging/logstash-1.1.13/logstash-1.1.13-monolithic.jar!/logstash/outputs/gelf.rb:193:in `receive'", "file:/usr/local/logging/logstash-1.1.13/logstash-1.1.13-monolithic.jar!/logstash/outputs/base.rb:55:in `handle'", "file:/usr/local/logging/logstash-1.1.13/logstash-1.1.13-monolithic.jar!/logstash/agent.rb:805:in `run_output'", "file:/usr/local/logging/logstash-1.1.13/logstash-1.1.13-monolithic.jar!/logstash/agent.rb:419:in `start_output'"], :level=>:warn}