OWFeatureStatistics: Fix crash when switching to data set with no target variable

Author: pavlin-policar

Orange/widgets/data/owfeaturestatistics.py

@@ -776,6 +776,7 @@ def set_data(self, data):
 
         if data is not None:
             self.color_var_model.set_domain(data.domain)
+            self.color_var = None
             if self.data.domain.class_vars:
                 self.color_var = self.data.domain.class_vars[0]
         else:

Orange/widgets/data/tests/test_owfeaturestatistics.py

@@ -264,6 +264,30 @@ def test_on_data_with_discrete_with_no_values(self, prepare_table):
         self.force_render_table()
         self.run_through_variables()
 
+    def test_switching_to_dataset_with_no_target_var(self):
+        """Switching from data set with target variable to a data set with
+        no target variable should not result in crash."""
+        data1 = make_table([continuous_full, ints_full], [ints_same, rgb_same])
+        data2 = make_table([rgb_full, ints_full])
+
+        self.send_signal(self.widget.Inputs.data, data1)
+        self.force_render_table()
+
+        self.send_signal(self.widget.Inputs.data, data2)
+        self.force_render_table()
+
+    def test_switching_to_dataset_with_target_var(self):
+        """Switching from data set with no target variable to a data set with
+        a target variable should not result in crash."""
+        data1 = make_table([rgb_full, ints_full])
+        data2 = make_table([continuous_full, ints_full], [ints_same, rgb_same])
+
+        self.send_signal(self.widget.Inputs.data, data1)
+        self.force_render_table()
+
+        self.send_signal(self.widget.Inputs.data, data2)
+        self.force_render_table()
+
 
 def select_rows(rows: List[int], widget: OWFeatureStatistics):
     """Since the widget sorts the rows, selecting rows isn't trivial."""