tests/owmds: Fix tests w.r.t. asynchronous execution

Author: ales-erjavec

Orange/widgets/unsupervised/tests/test_owmds.py

@@ -29,6 +29,10 @@ def setUp(self):
             }
         )  # type: OWMDS
 
+    def tearDown(self):
+        self.widget.onDeleteWidget()
+        super().tearDown()
+
     def _select_data(self):
         random.seed(42)
         points = random.sample(range(0, len(self.data)), 20)
@@ -56,7 +60,7 @@ def test_nan_plot(self):
         simulate.combobox_run_through_all(self.widget.cb_shape_value)
         simulate.combobox_run_through_all(self.widget.cb_size_value)
         simulate.combobox_run_through_all(self.widget.cb_label_value)
-
+        self.widget.stop()
         self.send_signal(self.widget.Inputs.data, None)
 
         data.X[:, 0] = np.nan