migrate_context: widgets crashed when migrating context without version

Author: VesnaT

Orange/widgets/settings.py

@@ -637,7 +637,8 @@ def _migrate_contexts(self, contexts):
             context = contexts[i]
             try:
                 self.widget_class.migrate_context(
-                    context, context.values.pop(VERSION_KEY, 0))
+                    context, context.values.pop(
+                        VERSION_KEY, self.widget_class.settings_version))
             except IncompatibleContext:
                 del contexts[i]
             except Exception:  # pylint: disable=broad-except

Orange/widgets/tests/base.py

@@ -839,6 +839,13 @@ def _compare_selected_annotated_domains(self, selected, annotated):
         annotated_vars = annotated.domain.variables + annotated.domain.metas
         self.assertLess(set(selected_vars), set(annotated_vars))
 
+    def test_migrate_context_without_version(self):
+        self.send_signal(self.signal_name, self.signal_data)
+        settings = self.widget.settingsHandler.pack_data(self.widget)
+        if "context_settings" in settings:
+            del settings["context_settings"][0].values["__version__"]
+        self.create_widget(self.widget.__class__, stored_settings=settings)
+
 
 class ProjectionWidgetTestMixin:
     """Class for projection widget testing"""
@@ -1017,6 +1024,12 @@ def test_send_report(self, timeout=DEFAULT_TIMEOUT):
         self.send_signal(self.widget.Inputs.data, None)
         self.widget.report_button.click()
 
+    def test_migrate_context_without_version(self):
+        self.send_signal(self.signal_name, self.signal_data)
+        settings = self.widget.settingsHandler.pack_data(self.widget)
+        del settings["context_settings"][0].values["__version__"]
+        self.create_widget(self.widget.__class__, stored_settings=settings)
+
 
 class AnchorProjectionWidgetTestMixin(ProjectionWidgetTestMixin):
     def test_embedding_missing_values(self):