fix timers

backend/app/api/routes_timer.py

@@ -63,11 +63,18 @@ def resume(session: DbSession, settings: Settings) -> dict:
 @router.post("/complete")
 def complete(body: CompleteTimerRequest, session: DbSession, settings: Settings) -> dict:
     try:
-        finished, follow_on = pomodoro.complete(session, settings, auto_next=body.auto_next)
+        finished, follow_on = pomodoro.complete(
+            session,
+            settings,
+            auto_next=body.auto_next,
+            expect_id=body.session_id,
+        )
     except pomodoro.TimerError as exc:
         raise HTTPException(status_code=400, detail=str(exc)) from exc
 
-    celebration = _maybe_celebrate(session, settings) if finished.is_work else None
+    # `finished` is None when the named interval was no longer the running one:
+    # nothing happened, so there is nothing to celebrate and nothing to announce.
+    celebration = _maybe_celebrate(session, settings) if finished and finished.is_work else None
     state = pomodoro.state(session, settings)
     state["finished"] = pomodoro.session_dict(finished)
     state["auto_started"] = pomodoro.session_dict(follow_on)