[file_crash_bug] KeyError: 'regressed_by' in detect_version_status_updates

[Suhaib Mujahid]

2023-07-13 12:44:21,953 - ERROR - Rule file_crash_bug
Traceback (most recent call last):
  File "/home/rm_bot/bugbot/bugbot/bzcleaner.py", line 844, in run
    self.send_email(date=date)
  File "/home/rm_bot/bugbot/bugbot/bzcleaner.py", line 763, in send_email
    data = self.get_email_data(date)
  File "/home/rm_bot/bugbot/bugbot/bzcleaner.py", line 681, in get_email_data
    bugs = self.get_bugs(date=date)
  File "/home/rm_bot/bugbot/bugbot/rules/file_crash_bug.py", line 181, in get_bugs
    updates = bug_analyzer.detect_version_status_updates()
  File "/home/rm_bot/bugbot/bugbot/bug/analyzer.py", line 119, in detect_version_status_updates
    if len(self._bug["regressed_by"]) > 1:
KeyError: 'regressed_by'