Confusing error message

I just spent a stupid amount of time trying to figure out why IpFire insisted a fixed lease had "invalid fixed ip address" when I could see nothing wrong with the address.

I had to read the source before I realized where the problem was: the same error message is also used when the *next-server* address is bad, and it doesn't accept server name there but wants an IP.

I guess this would not be the most critical thing to fix but at least changing the error message would be nice.