fix(server): accept the routed path in the index view

[Eljees]

Fixes #543

GET / returns HTTP 500 on a fresh install because the view function and its routes disagree:

@app.errorhandler(404)
@app.route('/', defaults={'text': ''})
@app.route('/<path:text>')
def index(ex):

Both routes supply text, and the error handler supplies ex, so Flask always calls index() with a keyword the signature doesn't accept:

TypeError: create_app.<locals>.index() got an unexpected keyword argument 'text'

This is the same one-line change that PR #537 made and that was lost when master was re-synced (see #543 for the archaeology; #541 was closed with a workaround that no longer helps, because master itself is broken).

Reproduced before and after

Minimal Flask app with exactly these decorators, python:3.12 / Flask 3:

master      GET /      -> 500
master      GET /a/b   -> 500
master      raises     -> TypeError: index() got an unexpected keyword argument 'text'
with fix    GET /      -> 200
with fix    GET /a/b   -> 200

ex=None, text=None keeps every existing caller working: the 404 handler still passes the exception, both routes still pass the captured path, and the body of the function is unchanged.

One note from the issue that is worth acting on separately: the fix needs to land on whichever internal branch master is synced from, otherwise it will be dropped again the next time.

AI-assisted (LLM used for drafting); the reproduction above was run and verified by me.