#247 declare globally the core gui variables (#250)

Co-authored-by: Fred Lefévère-Laoide <Fred.Lefevere-Laoide@Taipy.io>

src/taipy/gui_core/GuiCoreLib.py

@@ -474,9 +474,17 @@ class _GuiCore(ElementLibrary):
         return ["lib/taipy-gui-core.js"]
 
     def on_init(self, gui: Gui) -> t.Optional[t.Tuple[str, t.Any]]:
-        gui._add_adapter_for_type(_GuiCore.__SCENARIO_ADAPTER, _GuiCoreContext.scenario_adapter)
-        gui._add_adapter_for_type(_GuiCore.__DATANODE_ADAPTER, _GuiCoreContext.data_node_adapter)
-        return _GuiCore.__CTX_VAR_NAME, _GuiCoreContext(gui)
+        gui._get_default_locals_bind().update(
+            {
+                _GuiCoreContext._SCENARIO_SELECTOR_ERROR_VAR: "",
+                _GuiCoreContext._SCENARIO_SELECTOR_ID_VAR: "",
+                _GuiCoreContext._SCENARIO_VIZ_ERROR_VAR: "",
+            }
+        )
+        ctx = _GuiCoreContext(gui)
+        gui._add_adapter_for_type(_GuiCore.__SCENARIO_ADAPTER, ctx.scenario_adapter)
+        gui._add_adapter_for_type(_GuiCore.__DATANODE_ADAPTER, ctx.data_node_adapter)
+        return _GuiCore.__CTX_VAR_NAME, ctx
 
     def on_user_init(self, state: State):
         for var in [