core: check if ifa_addr field is set while trying to skip AF_PACKET interfaces

- reported by Juha Heinanen

socket_info.c

@@ -1207,7 +1207,7 @@ int add_interfaces(char* if_name, int family, unsigned short port,
 	{
 #ifdef AF_PACKET
 		/* skip AF_PACKET addr family since it is of no use later on */
-		if (ifa->ifa_addr->sa_family == AF_PACKET)
+		if (ifa->ifa_addr && ifa->ifa_addr->sa_family == AF_PACKET)
 			continue;
 #endif
 		if (if_name && strcmp(if_name, ifa->ifa_name))