Fixed #1785 -- debug view no longer assumes _get_lines_from_file returns None....

Fixed #1785 -- debug view no longer assumes _get_lines_from_file returns None. Thanks, django@binaryfeed.org

git-svn-id: http://code.djangoproject.com/svn/django/trunk@2864 bcc190cf-cafb-0310-a4f2-bffc1f526a37