Reflex ClientStateVar.set_value sets to undefined

[tim-haselhoff]

Describe the bug
A clear and concise description of what the bug is.
On click of the menu_trigger _on_open_change sets the value of the ClientStateVar to undefined instead of True

Is this a bug or am I just using call_function incorrectly with set_value?

To Reproduce
Steps to reproduce the behavior:

import reflex as rx
from reflex.event import EventSpec
from reflex.experimental import ClientStateVar

loading = ClientStateVar.create(default=False)


def index() -> rx.Component:
    def _on_open_change(is_open: rx.Var[bool]) -> list[EventSpec]:
        return [
            rx.call_function(loading.set_value(is_open)),
        ]

    return rx.el.div(
        rx.text(loading.value.to_string()),
        rx.menu.root(
            rx.menu.trigger(rx.button("open")),
            rx.menu.content(rx.text("hello :)")),
            on_open_change=_on_open_change,
        ),
    )


app = rx.App()
app.add_page(index)

• Code/Link to Repo:

Expected behavior
A clear and concise description of what you expected to happen.
_on_open_change sets the ClientStateVar to is_open.

Screenshots
If applicable, add screenshots to help explain your problem.

Specifics (please complete the following information):

• Python Version: 1.14.6
• Reflex Version: 0.9.6
• OS: Linux
• Browser (Optional): Chromium

Additional context
Add any other context about the problem here.

[linear-code]

ENG-10010