fix https://github.com/weseek/growi/pull/4899

packages/app/src/client/app.jsx

@@ -98,7 +98,7 @@ Object.assign(componentMappings, {
   'not-found-page': <NotFoundPage />,
   'not-found-alert': <NotFoundAlert
     isGuestUserMode={appContainer.isGuestUser}
-    isHidden={pageContainer.state.isNotCreatable || pageContainer.state.isTrashPage}
+    isHidden={pageContainer.state.pageId != null ? (pageContainer.state.isNotCreatable ?? pageContainer.state.isTrashPage) : false} // !!DO NOT MOVE THIS!! https://github.com/weseek/growi/pull/4899
   />,
 
   'forbidden-page': <ForbiddenPage />,