forge export fails when issue or message sender is "Nobody"
In some forge issues the sender is set to "Nobody", with no unix name, see, e.g: https://gforge.inria.fr/tracker/index.php?func=detail&aid=1847&group_id=157&atid=709
CreateGitlabIssuesFromGforge.py fails at:
issue['submitter_unixname'] = row3[0].find("./samp/a").text
(there's no <a>unixname</a>
in that case, find() returns None)
Same problem with the messages:
sender=pieces[0].find("./a").text
fails in get_all_messages_of_issue
.