Don't allow STATION_ELEV to be 0m if it's going to cause a quiet error
When configuring a new station I put in 0m for elevation because I'm very close to sea level but wasn't sure exactly what it is, and it turns out this is why my station was refusing to show up as active on the website, but it took quite a while to figure this out because systemctl status satnogs-client
was showing active
without errors. Please make it so 0m is either supported or an invalid entry so other people don't have to waste their time debugging.