fix: update segfault evaluation to reflect null pointer fixes

Co-authored-by: aider (deepseek/deepseek-reasoner) <aider@aider.chat>

evaluation.md

@@ -5,7 +5,7 @@
 | Category                 | Rating      | Remarks                                                                                                                                                         |
 |--------------------------|-------------|-----------------------------------------------------------------------------------------------------------------------------------------------------------------|
 | Mocked / Left Undone     | ✅ OK        | Multi‑channel and dynamic channel add/remove are now implemented. Control key (note 64) is handled as a modifier for command selection. Backward compatibility for note 1, 60, 61 retained. |
-| Potential Segfaults      | ✅ OK        | No obvious segfaults: all buffer accesses are bounds‑checked (e.g., `record_pos < LOOP_BUF_SIZE`), and null pointer checks exist.                               |
+| Potential Segfaults      | ✅ Fixed     | Added null checks for both `audio_in` and `audio_out` in the process callback, and `channel_add` no longer marks the channel active if port registration fails. |
 | Memory Safety            | ✅ OK        | No dynamic memory allocation; only a fixed‑size global buffer. No leaks, no use‑after‑free.                                                                     |
 | Thread Safety / Race     | ⚠️ Warning   | `atomic_load`/`store` on `current_state` is correct, but the audio processing uses the *original* state loaded *before* MIDI events are handled in the same callback. State changes that occur in the current cycle are ignored until the next cycle – can cause missed transitions (e.g., start recording one cycle late). |
 | Performance              | ✅ OK        | Linear buffer access, no system calls or allocations in the real‑time callback. Atomic operations are cheap. Fixed buffer size (0.96 MB) is safe.                |