Log disconnection with slave only when ip:port is available.

src/networking.c

@@ -670,10 +670,10 @@ void freeClient(redisClient *c) {
     if (c->flags & REDIS_SLAVE) {
         char ip[REDIS_IP_STR_LEN];
 
-        if (anetPeerToString(c->fd,ip,sizeof(ip),NULL) == -1)
-            strncpy(ip,"?",REDIS_IP_STR_LEN);
-        redisLog(REDIS_WARNING,"Connection with slave %s:%d lost.",
-            ip, c->slave_listening_port);
+        if (anetPeerToString(c->fd,ip,sizeof(ip),NULL) != -1) {
+            redisLog(REDIS_WARNING,"Connection with slave %s:%d lost.",
+                ip, c->slave_listening_port);
+        }
     }
 
     /* Free the query buffer */