test: narrow ZipStore path after file-object support

Author: AMBRA7592

tests/test_store/test_zip.py

@@ -93,6 +93,7 @@ async def test_serializable_store(self, store: ZipStore) -> None:
             pickle.dumps(store)
 
         store.close()
+        assert store.path is not None
         with zipfile.ZipFile(store.path, mode="r") as archive:
             assert archive.read("sentinel") == data.to_bytes()