Changes TextBoxBase to avoid setting selection ranges on unattached elements
(this either fails silently or throws an exception on most browsers).

Issue: 1385
Patch by: jgw
Review by: ajr (desk check)



git-svn-id: https://google-web-toolkit.googlecode.com/svn/trunk@2446 8db76d5a-ed1c-0410-87a9-c151d255dfc7