Clear active_plan_id in clear_all_filters()

Author: Mtk112

arho_feature_template/core/plan_manager.py

@@ -97,7 +97,8 @@ def load_land_use_plan(self):
             update_selected_plan(plan)
 
     def clear_all_filters(self):
-        """Clear filters for all vector layers in the project."""
+        """Clear active_plan_id and filters for all vector layers in the project."""
+        QgsExpressionContextUtils.setProjectVariable(QgsProject.instance(), "active_plan_id", None)
         for layer in QgsProject.instance().mapLayers().values():
             if isinstance(layer, QgsVectorLayer):
                 layer.setSubsetString("")