Upload w/o any file causes ClassCastException in Opera

In Tapestry v3.0-beta-3, submit a form with "Upload" component without actually
choosing any file will cause
"java.lang.ClassCastException" when browsing in Opera v7.23.

It works fine when browsing in IE6 and Mozilla Firefox 0.8.

The same issue exists in Workbench example web app (in Opera) - though in IE6
and Mozilla, it reports another exception, but that is another bug in the <input
jwcid="@Upload" .../> component - should be <input jwcid="inputFile@Upload" ...
/>.

Stack Trace:
*org.apache.tapestry.multipart.DefaultMultipartDecoder.
getUploadFile(DefaultMultipartDecoder.java:276)
*org.apache.tapestry.request.RequestContext.getUploadFile(RequestContext.java:
534)
*org.apache.tapestry.form.Upload.renderComponent(Upload.java:86)
*org.apache.tapestry.AbstractComponent.render(AbstractComponent.java:880)
*org.apache.tapestry.AbstractComponent.renderBody(AbstractComponent.java:657)
*org.apache.tapestry.form.Form.renderComponent(Form.java:396)
*org.apache.tapestry.AbstractComponent.render(AbstractComponent.java:880)
*org.apache.tapestry.form.Form.rewind(Form.java:602)
*org.apache.tapestry.engine.RequestCycle.rewindForm(RequestCycle.java:475)
*org.apache.tapestry.form.Form.trigger(Form.java:616)
*org.apache.tapestry.engine.DirectService.service(DirectService.java:210)
*org.apache.tapestry.engine.AbstractEngine.service(AbstractEngine.java:912)
*org.apache.tapestry.ApplicationServlet.doService(ApplicationServlet.java:238)
*org.apache.tapestry.ApplicationServlet.doPost(ApplicationServlet.java:367)
...