Merge pull request #2399 from jerneju/load-empty-data-paintdata

[FIX] Paint Data: Fix crash on empty data

Author: lanzagar

Orange/widgets/data/owpaintdata.py

@@ -797,7 +797,7 @@ def __init__(self):
         self.class_model.rowsInserted.connect(self._class_count_changed)
         self.class_model.rowsRemoved.connect(self._class_count_changed)
 
-        if self.data is None:
+        if not self.data:
             self.data = []
             self.__buffer = np.zeros((0, 3))
         elif isinstance(self.data, np.ndarray):

Orange/widgets/data/tests/test_owpaintdata.py

@@ -71,3 +71,10 @@ def test_sparse_data(self):
         self.assertTrue(self.widget.Warning.sparse_not_supported.is_shown())
         self.send_signal("Data", None)
         self.assertFalse(self.widget.Warning.sparse_not_supported.is_shown())
+
+    def test_load_empty_data(self):
+        """
+        It should not crash when old workflow with no data is loaded.
+        GH-2399
+        """
+        self.create_widget(OWPaintData, stored_settings={"data": []})