Directly register dynamic route args

Avoid the hack of adding a page that will fail to evaluate. This doesn't work
in recent reflex versions since page evaluation is delayed.

form-designer/form_designer/form_designer.py

@@ -24,12 +24,8 @@
 app = rx.App(theme=rx.theme(accent_color="blue"))
 app.add_page(home_page, route="/", title=constants.TITLE)
 
-# Adding a dummy route to register the dynamic route vars.
-with contextlib.suppress(ValueError):
-    app.add_page(
-        lambda: rx.fragment(on_click=rx.event.noop()),
-        route="/_dummy/[form_id]/[field_id]",
-    )
+# Register the dynamic route vars.
+rx.State.setup_dynamic_args(rx.app.get_route_args("/_dummy/[form_id]/[field_id]"))
 
 # Authentication via reflex-local-auth
 app.add_page(
@@ -97,4 +93,4 @@
 )
 
 # Create the database if it does not exist (hosting service does not migrate automatically)
-rx.Model.migrate()
+rx.Model.migrate()