posix_sockets: fix overflowing fd in close()

sys/net/gnrc/conn/udp/gnrc_conn_udp.c

@@ -56,6 +56,7 @@ void conn_udp_close(conn_udp_t *conn)
     assert(conn->l4_type == GNRC_NETTYPE_UDP);
     if (conn->netreg_entry.pid != KERNEL_PID_UNDEF) {
         gnrc_netreg_unregister(GNRC_NETTYPE_UDP, &conn->netreg_entry);
+        conn->netreg_entry.pid = KERNEL_PID_UNDEF;
     }
 }
 

sys/posix/sockets/posix_sockets.c

@@ -255,6 +255,7 @@ static int socket_close(int socket)
                         res = -1;
                         break;
                 }
+                break;
             default:
                 res = -1;
                 break;