Config: fix bug where active_session code be none therby throwing an error

src/aare/daq/config.py

@@ -135,7 +135,19 @@ class BeamlineConfig:
         with redis_lock.Lock(
             self.__client, f"{self.__bl}:active_session_lock", expire=10
         ):
-            if int(self.__client.get(f"{self.__bl}:active_session")) == session:
+            raw = self.__client.get(f"{self.__bl}:active_session")
+            if raw is None:
+                return
+            try:
+                active = int(raw)
+            except (TypeError, ValueError):
+                logger.warning(
+                    "Invalid active_session value in redis; ignoring",
+                    extra={"beamline": self.__bl, "raw": raw},
+                )
+                return
+
+            if active == session:
                 self.__client.delete(f"{self.__bl}:active_session")
 
     def force_set_active_session(self, session: int, expiry_sec: int) -> None: