fix: prevent overwriting saved queue with empty track lists in repository and music player

tests/test_queue_repository.py

@@ -20,6 +20,22 @@ class QueueRepositoryTest(unittest.TestCase):
             self.assertTrue((Path(directory) / "10.json").exists())
             self.assertTrue((Path(directory) / "20.json").exists())
 
+    def test_save_empty_tracks_does_nothing(self):
+        with tempfile.TemporaryDirectory() as directory:
+            repository = QueueRepository(directory)
+            tracks = [{"id": "first", "title": "First", "plays_left": 2}]
+
+            repository.save(10, tracks)
+            self.assertEqual(repository.load(10), tracks)
+
+            # Próba zapisania pustej listy nie powinna nadpisać poprzedniej
+            repository.save(10, [])
+            self.assertEqual(repository.load(10), tracks)
+
+            # Zapis pustej kolejki dla nowego serwera nie powinien tworzyć pliku
+            repository.save(20, [])
+            self.assertFalse(repository.exists(20))
+
 
 if __name__ == "__main__":
     unittest.main()