add new test for multiply extremes: label and history are None (#87)

test/test_data_handling/test_data_preparation.py

@@ -460,6 +460,11 @@ class TestDataPrep:
         data.make_labels("variables", "o3", "datetime", 2)
         assert data.multiply_extremes([1], extremes_on_right_tail_only=False) is None
 
+    def test_multiply_extremes_none_label_history(self,data ):
+        data.history = None
+        data.label = None
+        assert data.multiply_extremes([1], extremes_on_right_tail_only=False) is None
+
     def test_get_extremes_history(self, data):
         data.transform("datetime")
         data.make_history_window("variables", 3, "datetime")