rtrclient: Fix crash on empty ROA array

[ydahhrk]

Contribution description

When rtrclient's -e argument was included, the mustach interface was always attempting to access the ROA array, even when it was empty.

The array can be empty when the server returns a session that contains no prefix PDUs.

Testing procedure

I left a public server at fort-testing.dev.lacnic.net:8323.

Output before patch:

$ rtrclient -e tcp -pa fort-testing.dev.lacnic.net 8323
...
(2026/02/05 18:21:35:896903): RTR Socket: Sync successful, received 0 Prefix PDUs, 0 Router Key PDUs, 1 ASPA PDUs, session_id: 13155, SN: 1
(2026/02/05 18:21:35:896947): RTR_MGR: Group(1) status changed to: RTR_MGR_ESTABLISHED
(2026/02/05 18:21:35:896980): RTR Socket: State: RTR_ESTABLISHED
(2026/02/05 18:21:35:897009): RTR Socket: waiting 3600 sec. till next sync
Sync done
rtrclient: /home/ahhrk/git/rtrlib/./third-party/tommyds/tommyarray.h:97: tommy_array_ref: Assertion `pos < array->count' failed.
Aborted (core dumped)

Output after patch:

$ rtrclient -e tcp -pa fort-testing.dev.lacnic.net 8323
...
(2026/02/05 18:18:58:748383): RTR Socket: Sync successful, received 0 Prefix PDUs, 0 Router Key PDUs, 1 ASPA PDUs, session_id: 13155, SN: 1
(2026/02/05 18:18:58:748422): RTR_MGR: Group(1) status changed to: RTR_MGR_ESTABLISHED
(2026/02/05 18:18:58:748454): RTR Socket: State: RTR_ESTABLISHED
(2026/02/05 18:18:58:748481): RTR Socket: waiting 3600 sec. till next sync
Sync done

(2026/02/05 18:18:59:558883): RTR_MGR: rtr_mgr_stop()
(2026/02/05 18:18:59:558932): RTR Socket: rtr_stop()
(2026/02/05 18:18:59:558962): RTR_MGR: Calling rtr_mgr_cb with RTR_SHUTDOWN
(2026/02/05 18:18:59:558988): RTR_MGR: Received RTR_SHUTDOWN callback
(2026/02/05 18:18:59:559021): RTR_MGR: Group(1) status changed to: RTR_MGR_CLOSED
(2026/02/05 18:18:59:559048): RTR Socket: pthread_cancel()
(2026/02/05 18:18:59:559721): RTR Socket: pthread_join()
(2026/02/05 18:18:59:560149): TCP Transport(fort-testing.dev.lacnic.net:8323): Socket closed
 HOST:  fort-testing.dev.lacnic.net:8323
- ASPA 16777472 => [ 4294967295, 123, 70000 ]
(2026/02/05 18:18:59:560231): RTR Socket: Socket shut down
(2026/02/05 18:18:59:560260): RTR_MGR: rtr_mgr_free()
(2026/02/05 18:18:59:560296): TCP Transport(fort-testing.dev.lacnic.net:8323): Freeing socket

[Brias]

@ydahhrk Many thanks for this detailed and easy to test pull request. 🙏

I only have a few minor requests regarding code style and consistency, then we can merge this PR.

[ydahhrk]

Sorry... not sure what happened there.

The commit should be fixed now.

Some tests are failing. I will check next week why.