owheatmap: Fix inconsistent row_color_annotations

A combo box for choosing row annotation color is limited to metas and
class vars, and thus, when a selected feature was moved from metas to
attributes, an incompatible context would match.

That did not trigger any crashes because the combo box was updated
through special functions, but it did leave the UI in an inconsistent state:
an element with index of -1 was selected in the combo (""), and, the saved
color was still shown in the map.

Orange/widgets/visualize/owheatmap.py

@@ -146,9 +146,9 @@ class Outputs:
         selected_data = Output("Selected Data", Table, default=True)
         annotated_data = Output(ANNOTATED_DATA_SIGNAL_NAME, Table)
 
-    settings_version = 3
+    settings_version = 4
 
-    settingsHandler = settings.DomainContextHandler()
+    settingsHandler = settings.DomainContextHandlerPosition()
 
     # Disable clustering for inputs bigger than this
     MaxClustering = 25000
@@ -170,7 +170,7 @@ class Outputs:
     #: text row annotation (row names)
     annotation_var = settings.ContextSetting(None)
     #: color row annotation
-    annotation_color_var = settings.ContextSetting(None)
+    annotation_color_var = settings.ContextSetting(None, exclude_attributes=True)
     column_annotation_color_key: Optional[Tuple[str, str]] = settings.ContextSetting(None)
 
     # Discrete variable used to split that data/heatmaps (vertically)

Orange/widgets/visualize/tests/test_owheatmap.py

@@ -365,6 +365,20 @@ def test_row_color_annotations_with_na(self):
         widget.set_annotation_color_var(None)
         self.assertFalse(widget.scene.widget.right_side_colors[0].isVisible())
 
+    def test_row_color_annotations_invalid_context(self):
+        widget = self.widget
+        data = self.brown_selected[::5]
+        self.send_signal(widget.Inputs.data, data, widget=widget)
+        widget.set_annotation_color_var(data.domain["function"])
+        self.assertTrue(widget.scene.widget.right_side_colors[0].isVisible())
+        # attributes are ignored in for annotation_color_var, so the following
+        # data should not match any context
+        data_attributes = self.brown_selected.transform(
+            Domain(data.domain.attributes + data.domain.class_vars))
+        self.send_signal(widget.Inputs.data, data_attributes, widget=widget)
+        self.assertEqual(widget.row_side_color_cb.currentText(), "(None)")
+        self.assertFalse(widget.scene.widget.right_side_colors[0].isVisible())
+
     def test_col_color_annotations(self):
         widget = self.widget
         data = self._brown_selected_10()