Events search crashes on specific query

## internal server error if `host_ports=11`

https://mentat-hub.cesnet.cz/mentat/events/search?st_from=&st_to=&host_addrs=&host_ports=11&groups=abuse2%40spstrplz.cz&protocols=adb&description=aa&categories=Abusive.Spam&severities=low&detectors=cz.avcr.nemea.blacklist&detector_types=Auth&submit=Search