Fix missing title error for broken-site-report-ml job

[ksy36]

Since title is required there is an error when trying to process a batch of reports:

models.py", line 1021, in raise_for_status
    raise HTTPError(http_error_msg, response=self)
requests.exceptions.HTTPError: 400 Client Error: BAD REQUEST for url: https://bugbug.herokuapp.com/invalidcompatibilityreport/predict/broken_site_report/batch