logstash xmpp crash

$ java -jar logstash-1.2.1-flatjar.jar agent -f apache.conf
Using milestone 2 input plugin 'file'. This plugin should be stable, but if you see strange behavior, please let us know! For more information on plugin milestones, see http://logstash.net/docs/1.2.1/plugin-milestones {:level=>:warn}
Using milestone 2 output plugin 'xmpp'. This plugin should be stable, but if you see strange behavior, please let us know! For more information on plugin milestones, see http://logstash.net/docs/1.2.1/plugin-milestones {:level=>:warn}
D, [2013-09-10T11:39:04.109000 #8987] DEBUG -- : Debugging mode enabled.
W, [2013-09-10T11:39:04.110000 #8987]  WARN -- : Warnings mode enabled.
D, [2013-09-10T11:39:04.112000 #8987] DEBUG -- : CONNECTING:
    xmpp.netresearch.de:5222
D, [2013-09-10T11:39:04.125000 #8987] DEBUG -- : SENDING:
    <stream:stream xmlns:stream='http://etherx.jabber.org/streams' xmlns='jabber:client' to='netresearch.de' xml:lang='en' version='1.0' >
D, [2013-09-10T11:39:04.164000 #8987] DEBUG -- : RECEIVED:
    <stream:stream from='netresearch.de' id='ba8a635b-3986-4427-838c-82ae508bd068' xml:lang='en' xmlns:stream='http://etherx.jabber.org/streams' version='1.0' xmlns='jabber:client'/>
D, [2013-09-10T11:39:04.181000 #8987] DEBUG -- : FEATURES: waiting...
D, [2013-09-10T11:39:04.186000 #8987] DEBUG -- : RECEIVED:
    <stream:features><starttls xmlns='urn:ietf:params:xml:ns:xmpp-tls'><required/></starttls></stream:features>
D, [2013-09-10T11:39:04.188000 #8987] DEBUG -- : FEATURES: received
D, [2013-09-10T11:39:04.190000 #8987] DEBUG -- : FEATURES: waiting finished
D, [2013-09-10T11:39:04.192000 #8987] DEBUG -- : SENDING:
    <starttls xmlns='urn:ietf:params:xml:ns:xmpp-tls'/>
D, [2013-09-10T11:39:04.204000 #8987] DEBUG -- : RECEIVED:
    <proceed xmlns='urn:ietf:params:xml:ns:xmpp-tls'/>
D, [2013-09-10T11:39:04.208000 #8987] DEBUG -- : PROCESSING:
    <proceed xmlns='urn:ietf:params:xml:ns:xmpp-tls'/> (REXML::Element)
D, [2013-09-10T11:39:04.209000 #8987] DEBUG -- : TRYING stanzacbs...
D, [2013-09-10T11:39:04.210000 #8987] DEBUG -- : TRYING message/iq/presence/cbs...
Exception in thread "LogStash::Runner" org.jruby.exceptions.RaiseException: (NoMethodError) undefined method `error' for nil:NilClass
	at RUBY.to_s(file:/home/cweiske/bin/logstash/logstash-1.2.1-flatjar.jar!/xmpp4r/errors.rb:43)
	at RUBY.accept_features(file:/home/cweiske/bin/logstash/logstash-1.2.1-flatjar.jar!/xmpp4r/connection.rb:111)
	at RUBY.connect(file:/home/cweiske/bin/logstash/logstash-1.2.1-flatjar.jar!/xmpp4r/connection.rb:79)
	at RUBY.connect(file:/home/cweiske/bin/logstash/logstash-1.2.1-flatjar.jar!/xmpp4r/client.rb:70)
	at RUBY.connect(file:/home/cweiske/bin/logstash/logstash-1.2.1-flatjar.jar!/logstash/outputs/xmpp.rb:55)
	at RUBY.register(file:/home/cweiske/bin/logstash/logstash-1.2.1-flatjar.jar!/logstash/outputs/xmpp.rb:35)
	at org.jruby.RubyArray.each(org/jruby/RubyArray.java:1617)
	at RUBY.outputworker(file:/home/cweiske/bin/logstash/logstash-1.2.1-flatjar.jar!/logstash/pipeline.rb:208)
	at RUBY.start_outputs(file:/home/cweiske/bin/logstash/logstash-1.2.1-flatjar.jar!/logstash/pipeline.rb:140)

$ java -version
java version "1.7.0_25"
OpenJDK Runtime Environment (IcedTea 2.3.10) (7u25-2.3.10-1ubuntu0.13.04.2)
OpenJDK 64-Bit Server VM (build 23.7-b01, mixed mode)