nullable Date ends up in a java.util.ConcurrentModificationException

From the domain Class Person I generated controller and views by generate-all command
then I started the applicatin

peter@amd64Koala:~/NullDate$ grails run-app
Welcome to Grails 1.2.0 - http://grails.org/
Licensed under Apache Standard License 2.0
Grails home is set to: /opt/grails/grails-1.2.0

Base Directory: /home/peter/NullDate
Resolving dependencies...
Dependencies resolved in 622ms.
Running script /opt/grails/grails-1.2.0/scripts/RunApp.groovy
Environment set to development
[delete] Deleting directory /home/peter/.grails/1.2.0/projects/NullDate/tomcat
Running Grails application..
Server running. Browse to http://localhost:8080/NullDate

Entering a NullDate leads to the following stacktrace

2009-12-27 12:11:01,877 [http-8080-2] ERROR errors.GrailsExceptionResolver - null
java.util.ConcurrentModificationException
at java.util.LinkedHashMap$LinkedHashIterator.nextEntry(LinkedHashMap.java:373)
at java.util.LinkedHashMap$KeyIterator.next(LinkedHashMap.java:384)
at java.lang.Thread.run(Thread.java:619)
2009-12-27 12:11:01,995 [http-8080-2] ERROR [Tomcat].[localhost] - Exception Processing ErrorPage[errorCode=500, location=/grails-errorhandler]
java.lang.IllegalStateException: Cannot reset buffer after response has been committed
at org.apache.catalina.connector.Response.resetBuffer(Response.java:691)
at org.apache.catalina.core.StandardHostValve.custom(StandardHostValve.java:409)
at org.apache.catalina.core.StandardHostValve.status(StandardHostValve.java:343)
at org.apache.catalina.core.StandardHostValve.throwable(StandardHostValve.java:287)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:142)
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:293)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:849)
at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:583)
at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:454)
at java.lang.Thread.run(Thread.java:619)

peter
from Dortmund Germany