flet + fast_api always return http 200 OK or 302 even when path does not exist

Hi,

I'm experiencing the following issue with flet, flet-fastapi and uvicorn. The application always returns http 200 ok response when I would expect a 404 response I used following example app:

import flet as ft
import flet_fastapi


async def root_main(page: ft.Page):
    await page.add_async(ft.Text("This is root app!"))


async def sub_main(page: ft.Page):
    await page.add_async(ft.Text("This is sub app!"))


app = flet_fastapi.FastAPI()


app.mount("/sub-app", flet_fastapi.app(sub_main))
app.mount("/", flet_fastapi.app(root_main))

When browsing to something like http:\localhost\invalidurl I still get http response 200. How can I get HTTP response 404?

Reproduce the response behavior with the example using flet_fastapi.FastAPI, the two app.mount calls, and Uvicorn, including an invalid path. Trace how the mounted root and sub-app routes handle unmatched paths; done means invalid URLs return HTTP 404 instead of 200 or 302 without breaking the valid routes.