removed all uses of undefined from code base

It's a code smell, can lead to hard to diagnose error messages.

Assistant/Pairing/Network.hs

@@ -33,9 +33,9 @@ pairingPort = 55556
 {- Goal: Reach all hosts on the same network segment.
  - Method: Use same address that avahi uses. Other broadcast addresses seem
  - to not be let through some routers. -}
-multicastAddress :: SomeAddr -> HostName
-multicastAddress (IPv4Addr _) = "224.0.0.251"
-multicastAddress (IPv6Addr _) = "ff02::fb"
+multicastAddress :: AddrClass -> HostName
+multicastAddress IPv4AddrClass = "224.0.0.251"
+multicastAddress IPv6AddrClass = "ff02::fb"
 
 {- Multicasts a message repeatedly on all interfaces, with a 2 second
  - delay between each transmission. The message is repeated forever
@@ -62,7 +62,7 @@ multicastPairMsg repeats secret pairdata stage = go M.empty repeats
 	sendinterface cache i = void $ tryIO $
 		withSocketsDo $ bracket setup cleanup use
 	  where
-		setup = multicastSender (multicastAddress i) pairingPort
+		setup = multicastSender (multicastAddress IPv4AddrClass) pairingPort
 		cleanup (sock, _) = sClose sock -- FIXME does not work
 		use (sock, addr) = do
 			setInterface sock (showAddr i)