fix: SQL error when user ID missing

[Rom1-B]

Changes description

Prevent SQL error :

  Error: You have an error in your SQL syntax; check the manual that corresponds to your MariaDB server version for the right syntax to use near ') AND  ( glpi_plugin_formcreator_issues.entities_id = '0'  )  AND (   `gl...' at line 48
  Backtrace :
  src/Search.php:1460                                DBmysql->doQuery()
  src/SavedSearch.php:1340                           Search::constructData()
  src/SavedSearch.php:1266                           SavedSearch->execute()
  src/CronTask.php:1035                              SavedSearch::croncountAll()
  front/cron.php:87                                  CronTask::launch()

Checklist

Please check if your PR fulfills the following specifications:

• Tests for the changes have been added
• Docs have been added/updated

References

ref !33894