[FIX] Select Rows: None on output when no data

Orange/widgets/data/owselectrows.py

@@ -530,6 +530,11 @@ def commit(self):
                 matching_output = remover(matching_output)
                 non_matching_output = remover(non_matching_output)
 
+        if matching_output is not None and not len(matching_output):
+            matching_output = None
+        if non_matching_output is not None and not len(non_matching_output):
+            non_matching_output = None
+
         self.Outputs.matching_data.send(matching_output)
         self.Outputs.unmatched_data.send(non_matching_output)
 

Orange/widgets/data/tests/test_owselectrows.py

@@ -242,3 +242,20 @@ def widget_with_context(self, domain, conditions):
         settings = dict(context_settings=[context])
 
         return self.create_widget(OWSelectRows, settings)
+
+    def test_output_filter(self):
+        """
+        None on output when there is no data.
+        GH-2726
+        """
+        data = Table("iris")[:10]
+        len_data = len(data)
+        self.send_signal(self.widget.Inputs.data, data)
+
+        self.enterFilter(data.domain[0], "is below", "-1")
+        self.assertIsNone(self.get_output("Matching Data"))
+        self.assertEqual(len(self.get_output("Unmatched Data")), len_data)
+        self.widget.remove_all_button.click()
+        self.enterFilter(data.domain[0], "is below", "10")
+        self.assertIsNone(self.get_output("Unmatched Data"))
+        self.assertEqual(len(self.get_output("Matching Data")), len_data)