Fixed #6423 -- Don't fall in a hole in the debug screen if somebody raises an...

Fixed #6423 -- Don't fall in a hole in the debug screen if somebody raises an old-fashioned string exception. Thanks, guettli.


git-svn-id: http://code.djangoproject.com/svn/django/trunk@7065 bcc190cf-cafb-0310-a4f2-bffc1f526a37