logstash 2.0.0: RuntimeError: can't add a new key into hash during iteration

OS: CentOS 7.1
Logstash: 2.0.0
Java: OpenJDK 1.8.0_65

Filter:
filter {

if [type] == 'accesslog' {
grok{
match => {'message' => "%{COMBINEDAPACHELOG} - %{NUMBER:responseTime} ms"}
}

```
kv {
source => 'request'
field_split => "&?"
}

urldecode{
all_fields => true
}

mutate{
split => {
'search_text' => " "
'tags' => "+"
}
}

date{
match => ['timestamp' , "dd/MMM/yyyy:HH:mm:ss Z"]
}
```

}

}

logstash.err:
RuntimeError: can't add a new key into hash during iteration
[]= at org/jruby/RubyHash.java:992
find_or_create_target at /opt/logstash/vendor/bundle/jruby/1.9/gems/logstash-core-2.0.0-java/lib/logstash/util/accessors.rb:119
each at org/jruby/RubyArray.java:1613
inject at org/jruby/RubyEnumerable.java:852
find_or_create_target at /opt/logstash/vendor/bundle/jruby/1.9/gems/logstash-core-2.0.0-java/lib/logstash/util/accessors.rb:119
lookup_or_create at /opt/logstash/vendor/bundle/jruby/1.9/gems/logstash-core-2.0.0-java/lib/logstash/util/accessors.rb:98
set at /opt/logstash/vendor/bundle/jruby/1.9/gems/logstash-core-2.0.0-java/lib/logstash/util/accessors.rb:63
[]= at /opt/logstash/vendor/bundle/jruby/1.9/gems/logstash-core-2.0.0-java/lib/logstash/event.rb:146
filter at /opt/logstash/vendor/bundle/jruby/1.9/gems/logstash-filter-urldecode-2.0.2/lib/logstash/filters/urldecode.rb:36
each at org/jruby/RubyHash.java:1342
filter at /opt/logstash/vendor/bundle/jruby/1.9/gems/logstash-filter-urldecode-2.0.2/lib/logstash/filters/urldecode.rb:36
multi_filter at /opt/logstash/vendor/bundle/jruby/1.9/gems/logstash-core-2.0.0-java/lib/logstash/filters/base.rb:152
each at org/jruby/RubyArray.java:1613
multi_filter at /opt/logstash/vendor/bundle/jruby/1.9/gems/logstash-core-2.0.0-java/lib/logstash/filters/base.rb:149
cond_func_5 at (eval):326
each at org/jruby/RubyArray.java:1613
cond_func_5 at (eval):321
filter_func at (eval):239
filterworker at /opt/logstash/vendor/bundle/jruby/1.9/gems/logstash-core-2.0.0-java/lib/logstash/pipeline.rb:219
start_filters at /opt/logstash/vendor/bundle/jruby/1.9/gems/logstash-core-2.0.0-java/lib/logstash/pipeline.rb:154

Kind Regards
Michael