Fix NoneType crash in LLM plural check when OpenRouter returns null content

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

cheddahbot/scheduler.py

@@ -134,7 +134,7 @@ class Scheduler:
                 timeout=15,
             )
             resp.raise_for_status()
-            answer = resp.json()["choices"][0]["message"]["content"].strip()
+            answer = (resp.json()["choices"][0]["message"]["content"] or "").strip()
             result = "YES" in answer.upper()
             log.debug("LLM plural check: '%s' vs '%s' ->%s (%s)", a, b, result, answer)
         except Exception as e: