error in JS console on Chrome

[smida02]

I use the following technique to download files from the server

public void onSuccess(Object result) {            

                String reportName = (String)result;                

                String url = GWT.getModuleBaseURL() + "ReportUploadHandler" + "?rname=" + reportName;

                Frame frame = new Frame(url);

                frame.setVisible(false);                

                RootPanel.get().add(frame);                

}

It works fine on both Fire Fox and Chrome. However, sometimes on Chrome I see an error in the console saying

'cannot read property 'offsetwidth' of null' the error is often listed multiple times.

Its strange because often the exact code runs fine with no errors in the console. BTW, I have never seen this on Fire Fox.

Any ideas?