Only send JOIN message if we have channels to join

Don't send a JOIN command to upstream server when no channels are configured.

upstream.go

@@ -552,19 +552,21 @@ func (uc *upstreamConn) handleMessage(msg *irc.Message) error {
 			dc.updateSupportedCaps()
 		})
 
-		// TODO: split this into multiple messages if need be
-		var names, keys []string
-		for _, ch := range uc.network.channels {
-			names = append(names, ch.Name)
-			keys = append(keys, ch.Key)
+		if len(uc.network.channels) > 0 {
+			// TODO: split this into multiple messages if need be
+			var names, keys []string
+			for _, ch := range uc.network.channels {
+				names = append(names, ch.Name)
+				keys = append(keys, ch.Key)
+			}
+			uc.SendMessage(&irc.Message{
+				Command: "JOIN",
+				Params: []string{
+					strings.Join(names, ","),
+					strings.Join(keys, ","),
+				},
+			})
 		}
-		uc.SendMessage(&irc.Message{
-			Command: "JOIN",
-			Params: []string{
-				strings.Join(names, ","),
-				strings.Join(keys, ","),
-			},
-		})
 	case irc.RPL_MYINFO:
 		if err := parseMessageParams(msg, nil, &uc.serverName, nil, &uc.availableUserModes, nil); err != nil {
 			return err