fix: use valid buffer in recv() instead of NULL

src/server/server.c

@@ -478,7 +478,7 @@ _shutdown(void)
     parser_close();
 
     shutdown(listen_socket, 2);
-    while (recv(listen_socket, NULL, 1, 0) > 0) {}
+    char _discard; while (recv(listen_socket, &_discard, 1, 0) > 0) {}
     close(listen_socket);
 
     prime_free_all();