Tvheadend

Most likely the user manually hacked the configuration files or possibly something went wrong during config migration?

But yeah a simple validation on load would probably not be a bad idea. The only thing I'd say is you start here and you'll end up with needing validation all over the shop! TVH generally takes a pretty light approach to configuration validation, there are various reasons for this (mainly because we're lazy), but also because its intended to be used by people that have a vague idea of what they're doing but checks usually exist at point of entry rather than when loading the config.