fix: race condition on shared account info causes KeyError during download

[waldh4ri]

Problem

BaseAccount.choose() clears self.info before resyncing it for the newly selected user:

self.user = user
self.info.clear()
self.req.close()
...
if not self.logged:
    self.relogin()

The account plugin instance is shared across every download thread for a given hoster (AccountManager.get_account_plugin caches a single instance per plugin). Downloader plugins read self.account.info["login"]["password"] directly, without holding the account's lock.

When one thread runs choose() and clears info while another thread is mid-download reading from it, the reader can observe an empty dict and crash:

File "pyload/plugins/downloaders/AlldebridCom.py", line 83, in handle_premium
    "apikey": self.account.info["login"]["password"],
              ~~~~~~~~~~~~~~~~~^^^^^^^^^^
KeyError: 'login'

This affects every downloader that reads account.info["login"][...] directly (AlldebridCom, PremiumizeMe, RealDebrid, TorboxApp, FikperCom, ZeveraCom, and others), and shows up intermittently under concurrent downloads, causing some files in a batch to fail while others succeed.

A prior change (add some more locks) added @lock to login(), logout(), and sync(), but the readers in the downloader plugins never acquire that lock, so the empty-dict window was never actually closed.

Fix

Replace self.info.clear() with self.sync(). sync() already runs a few lines later via the self.logged check, so the explicit clear is redundant. Calling sync() directly rebuilds info["login"]/info["data"] for the new user in place, so self.info transitions straight from the old user's data to the new user's data and is never left empty for a reader on another thread to observe.

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[GammaC0de]

i think calling clear() and then sync() would be better, please check and report

[waldh4ri]

That would reintroduce the race (with a shorter window) and could lead to the same KeyError. self.info update mechanism must be atomic because we don't acquire self.account.lock before reading info in any of hoster.py/AlldebridCom.py/etc. sync update to info is atomic and never leave it in a blank state:

d = {"login": {}, "data": {}}
for k, v in u.items():
    ...
self.info.update(d)