description:
exception is thrown out when tick "allow multiple values".

build number:
2.5.2.v20100106-0630

steps to reproduce:
1. new a report parameter.
2. select "list box".
3. tick "allow multiple values".

expected result:
no exception.

actual result:
exception is thrown out.
error log:
org.eclipse.swt.swtexception: widget is disposed
at org.eclipse.swt.swt.error(swt.java:3884)
at org.eclipse.swt.swt.error(swt.java:3799)
at org.eclipse.swt.swt.error(swt.java:3770)
at org.eclipse.swt.widgets.widget.error(widget.java:463)
at org.eclipse.swt.widgets.widget.checkwidget(widget.java:336)
at org.eclipse.swt.widgets.control.getlayoutdata(control.java:1266)
at org.eclipse.birt.report.designer.internal.ui.util.widgetutil.setexcludegriddata(widgetutil.java:211)
at org.eclipse.birt.report.designer.ui.dialogs.parameterdialog.initdefaultvalueviewer(parameterdialog.java:4301)
at org.eclipse.birt.report.designer.ui.dialogs.parameterdialog.access$22(parameterdialog.java:4281)
at org.eclipse.birt.report.designer.ui.dialogs.parameterdialog$14.widgetselected(parameterdialog.java:949)
at org.eclipse.swt.widgets.typedlistener.handleevent(typedlistener.java:228)
at org.eclipse.swt.widgets.eventtable.sendevent(eventtable.java:84)
at org.eclipse.swt.widgets.widget.sendevent(widget.java:1003)
at org.eclipse.swt.widgets.display.rundeferredevents(display.java:3880)
at org.eclipse.swt.widgets.display.readanddispatch(display.java:3473)
at org.eclipse.jface.window.window.runeventloop(window.java:825)
at org.eclipse.jface.window.window.open(window.java:801)
at org.eclipse.birt.report.designer.ui.dialogs.basetitleareadialog.open(basetitleareadialog.java:193)
at org.eclipse.birt.report.designer.internal.ui.views.data.providers.parametersnodeprovider.createelement(parametersnodeprovider.java:116)
at org.eclipse.birt.report.designer.internal.ui.views.defaultnodeprovider.createelement(defaultnodeprovider.java:642)
at org.eclipse.birt.report.designer.internal.ui.views.defaultnodeprovider.performinsert(defaultnodeprovider.java:687)
at org.eclipse.birt.report.designer.internal.ui.views.data.providers.parametersnodeprovider.performinsert(parametersnodeprovider.java:138)
at org.eclipse.birt.report.designer.internal.ui.views.defaultnodeprovider.performrequest(defaultnodeprovider.java:410)
at org.eclipse.birt.report.designer.internal.ui.views.actions.insertaction.doaction(insertaction.java:210)
at org.eclipse.birt.report.designer.internal.ui.views.actions.abstractelementaction.run(abstractelementaction.java:70)
at org.eclipse.jface.action.action.runwithevent(action.java:498)
at org.eclipse.jface.action.actioncontributionitem.handlewidgetselection(actioncontributionitem.java:584)
at org.eclipse.jface.action.actioncontributionitem.access$2(actioncontributionitem.java:501)
at org.eclipse.jface.action.actioncontributionitem$5.handleevent(actioncontributionitem.java:411)
at org.eclipse.swt.widgets.eventtable.sendevent(eventtable.java:84)
at org.eclipse.swt.widgets.widget.sendevent(widget.java:1003)
at org.eclipse.swt.widgets.display.rundeferredevents(display.java:3880)
at org.eclipse.swt.widgets.display.readanddispatch(display.java:3473)
at org.eclipse.ui.internal.workbench.runeventloop(workbench.java:2405)
at org.eclipse.ui.internal.workbench.runui(workbench.java:2369)
at org.eclipse.ui.internal.workbench.access$4(workbench.java:2221)
at org.eclipse.ui.internal.workbench$5.run(workbench.java:500)
at org.eclipse.core.databinding.observable.realm.runwithdefault(realm.java:332)
at org.eclipse.ui.internal.workbench.createandrunworkbench(workbench.java:493)
at org.eclipse.ui.platformui.createandrunworkbench(platformui.java:149)
at org.eclipse.ui.internal.ide.application.ideapplication.start(ideapplication.java:113)
at org.eclipse.equinox.internal.app.eclipseapphandle.run(eclipseapphandle.java:194)
at org.eclipse.core.runtime.internal.adaptor.eclipseapplauncher.runapplication(eclipseapplauncher.java:110)
at org.eclipse.core.runtime.internal.adaptor.eclipseapplauncher.start(eclipseapplauncher.java:79)
at org.eclipse.core.runtime.adaptor.eclipsestarter.run(eclipsestarter.java:368)
at org.eclipse.core.runtime.adaptor.eclipsestarter.run(eclipsestarter.java:179)
at sun.reflect.nativemethodaccessorimpl.invoke0(native method)
at sun.reflect.nativemethodaccessorimpl.invoke(nativemethodaccessorimpl.java:39)
at sun.reflect.delegatingmethodaccessorimpl.invoke(delegatingmethodaccessorimpl.java:25)
at java.lang.reflect.method.invoke(method.java:585)
at org.eclipse.equinox.launcher.main.invokeframework(main.java:559)
at org.eclipse.equinox.launcher.main.basicrun(main.java:514)
at org.eclipse.equinox.launcher.main.run(main.java:1311)

fixed it.
verified in build (2.5.2.v20100113-0630), closed.