Prevent error entirely

Co-authored-by: Simon H <5968653+dummdidumm@users.noreply.github.com>

src/runtime/store/index.ts

@@ -99,11 +99,8 @@ export function writable<T>(value?: T, start: StartStopNotifier<T> = noop): Writ
 		return () => {
 			subscribers.delete(subscriber);
 			if (subscribers.size === 0) {
-				if (stop === null) {
-					throw new Error('unsubscribe cannot be called twice');
-				}
 				stop();
-				stop = null;
+				stop = noop;
 			}
 		};
 	}