Grails export plugin strange behavior, errs only on PDF, others fine -

i using exporter plugin1.6 grails 2.3.8 , controller's list method:

def list () {     println "*** list method called."     println "*** params: " + params     if(!params.max) params.max = 10      if(params?.exportformat && params.exportformat != "html"){         response.contenttype = grailsapplication.config.grails.mime.types[params.exportformat]         response.setheader("content-disposition", "attachment; filename=chairs.${params.extension}")          list fields = ["constructionmaterials"]         map labels = ["constructionmaterials": "construction materials"]         // formatter closure         def uppercase = { domain, value ->             return value.touppercase()         }          map formatters = [constructionmaterials: uppercase]         map parameters = [constructionmaterials: "cool chairs", "column.widths": [0.2, 0.3, 0.5]]         println "*** make here?"         exportservice.export(params.exportformat, response.outputstream,chair.list(params), fields, labels, formatters, parameters)     }      [ chairinstancelist: chair.list( params ) ] } 

it works fine when click on csv , xml when click on pdf error.

| error 2014-06-26 01:47:49,139 [http-bio-8080-exec-8] error [/demoapp].[default]  - servlet.service() servlet [default] in context path [/demoapp] threw exception [org.springframework.web.util.nestedservletexception: request processing failed; nested exception groovy.lang.missingmethodexception: no signature of method: static java.lang.math.max() applicable argument types: (java.lang.integer, null) values: [4, null] possible solutions: max(int, int), max(double, double), max(float, float), max(long, long), min(int, int), wait()] root cause message: no signature of method: static java.lang.math.max() applicable argument types: (java.lang.integer, null) values: [4, null] possible solutions: max(int, int), max(double, double), max(float, float), max(long, long), min(int, int), wait()     line | method ->>  251 | doappend              in org.apache.log4j.appenderskeleton - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - |     66 | appendlooponappenders in org.apache.log4j.helpers.appenderattachableimpl |    206 | callappenders . . . . in org.apache.log4j.category |    391 | forcedlog             in     '' |    856 | log . . . . . . . . . in     '' |    192 | logmessage            in org.slf4j.impl.grailslog4jloggeradapter |    167 | error . . . . . . . . in     '' |    213 | error                 in org.apache.commons.logging.impl.slf4jlog |    198 | dofilter . . . . . .  in grails.plugin.cache.web.filter.pagefragmentcachingfilter |     63 | dofilter              in grails.plugin.cache.web.filter.abstractfilter |   1145 | runworker . . . . . . in java.util.concurrent.threadpoolexecutor |    615 | run                   in java.util.concurrent.threadpoolexecutor$worker ^    744 | run . . . . . . . . . in java.lang.thread 

why export 2 formats fine err on pdf?

update: ok weird think pdf option works when have more 4 domain instances. not when number equal or below that. can explain? , when work this file get. , this equivalent xml file get.