bug: `page.vertical_alignment = CENTER` stops vertically centering content when `page.scroll` is enabled

[ndonkoHenri]

When page.scroll is set, even to ft.ScrollMode.HIDDEN, page.vertical_alignment = ft.MainAxisAlignment.CENTER no longer centers page content vertically. The content remains horizontally centered, but it is positioned near the top of the page.

Originally reported on Discord.

Repro

import flet as ft


def main(page: ft.Page):
    page.horizontal_alignment = ft.CrossAxisAlignment.CENTER
    page.vertical_alignment = ft.MainAxisAlignment.CENTER
    page.scroll = ft.ScrollMode.HIDDEN

    page.add(ft.Text("Center"))


if __name__ == "__main__":
    ft.run(main)

Expected behavior

The text should be centered both horizontally and vertically, matching behavior when page.scroll is not set.

Actual behavior

The text is centered horizontally, but appears near the top vertically.