fixup! sys/net/application_layer/gcoap: keep request on observe notif…

…ication

sys/net/application_layer/gcoap/gcoap.c

@@ -524,8 +524,9 @@ static void _process_coap_pdu(gcoap_socket_t *sock, sock_udp_ep_t *remote, sock_
 
                 /* The memo must be kept if the response is an observe notification.
                  * Non-2.xx notifications indicate that the associated observe entry
-                 * was removed on the server side. Then also remove it here. */
+                 * was removed on the server side. Then also free the memo here. */
                 if (!observe_notification || (code_class != COAP_CLASS_SUCCESS)) {
+                    /* setting the state to unused frees (drops) the memo entry */
                     memo->state = GCOAP_MEMO_UNUSED;
                 }