Carrot2

javax.servlet.ServletException: java.util.ConcurrentModificationException
	at org.carrot2.webapp.QueryProcessorServlet.doGet(QueryProcessorServlet.java:221)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:617)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
	at org.carrot2.util.xsltfilter.XSLTFilter.doFilter(XSLTFilter.java:131)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
	at com.planetj.servlet.filter.compression.CompressingFilter.doFilter(CompressingFilter.java:270)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
	at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233)
	at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)
	at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127)
	at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
	at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
	at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:298)
	at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:852)
	at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:588)
	at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:489)
	at java.lang.Thread.run(Thread.java:619)
Caused by: java.util.ConcurrentModificationException
	at java.util.AbstractList$Itr.checkForComodification(AbstractList.java:372)
	at java.util.AbstractList$Itr.next(AbstractList.java:343)
	at org.simpleframework.xml.core.CompositeInlineList.write(CompositeInlineList.java:254)
	at org.simpleframework.xml.core.CompositeInlineList.write(CompositeInlineList.java:239)
	at org.simpleframework.xml.core.Composite.writeElement(Composite.java:1175)
	at org.simpleframework.xml.core.Composite.writeElement(Composite.java:1156)
	at org.simpleframework.xml.core.Composite.writeElements(Composite.java:1037)
	at org.simpleframework.xml.core.Composite.write(Composite.java:943)
	at org.simpleframework.xml.core.Composite.write(Composite.java:919)
	at org.simpleframework.xml.core.Composite.writeElement(Composite.java:1175)
	at org.simpleframework.xml.core.Composite.writeElement(Composite.java:1156)
	at org.simpleframework.xml.core.Composite.writeElements(Composite.java:1037)
	at org.simpleframework.xml.core.Composite.write(Composite.java:943)
	at org.simpleframework.xml.core.Composite.write(Composite.java:919)
	at org.simpleframework.xml.core.Traverser.write(Traverser.java:236)
	at org.simpleframework.xml.core.CompositeInlineList.write(CompositeInlineList.java:262)
	at org.simpleframework.xml.core.CompositeInlineList.write(CompositeInlineList.java:239)
	at org.simpleframework.xml.core.Composite.writeElement(Composite.java:1175)
	at org.simpleframework.xml.core.Composite.writeElement(Composite.java:1156)
	at org.simpleframework.xml.core.Composite.writeElements(Composite.java:1037)
	at org.simpleframework.xml.core.Composite.write(Composite.java:943)
	at org.simpleframework.xml.core.Composite.write(Composite.java:919)
	at org.simpleframework.xml.core.Traverser.write(Traverser.java:236)
	at org.simpleframework.xml.core.CompositeValue.write(CompositeValue.java:189)
	at org.simpleframework.xml.core.CompositeInlineMap.write(CompositeInlineMap.java:250)
	at org.simpleframework.xml.core.CompositeInlineMap.write(CompositeInlineMap.java:225)
	at org.simpleframework.xml.core.Composite.writeElement(Composite.java:1175)
	at org.simpleframework.xml.core.Composite.writeElement(Composite.java:1156)
	at org.simpleframework.xml.core.Composite.writeElements(Composite.java:1037)
	at org.simpleframework.xml.core.Composite.write(Composite.java:943)
	at org.simpleframework.xml.core.Composite.write(Composite.java:919)
	at org.simpleframework.xml.core.Composite.writeElement(Composite.java:1175)
	at org.simpleframework.xml.core.Composite.writeElement(Composite.java:1156)
	at org.simpleframework.xml.core.Composite.writeElements(Composite.java:1037)
	at org.simpleframework.xml.core.Composite.write(Composite.java:943)
	at org.simpleframework.xml.core.Composite.write(Composite.java:919)
	at org.simpleframework.xml.core.Traverser.write(Traverser.java:236)
	at org.simpleframework.xml.core.Traverser.write(Traverser.java:208)
	at org.simpleframework.xml.core.Traverser.write(Traverser.java:186)
	at org.simpleframework.xml.core.Persister.write(Persister.java:1187)
	at org.simpleframework.xml.core.Persister.write(Persister.java:1169)
	at org.simpleframework.xml.core.Persister.write(Persister.java:1147)
	at org.simpleframework.xml.core.Persister.write(Persister.java:1266)
	at org.carrot2.webapp.QueryProcessorServlet.handleSearchRequest(QueryProcessorServlet.java:414)
	at org.carrot2.webapp.QueryProcessorServlet.doGet(QueryProcessorServlet.java:216)