Correctly handle account with invalid access token

Show a popup saying the session was signed out and cleanup
the models data, instead of spamming the users with
never-ending errors.

src/backend/backend.py

@@ -18,7 +18,7 @@ from appdirs import AppDirs
 import nio
 
 from . import __app_name__
-from .errors import MatrixError
+from .errors import MatrixError, MatrixInvalidAccessToken
 from .matrix_client import MatrixClient
 from .media_cache import MediaCache
 from .models import SyncId
@@ -305,6 +305,11 @@ class Backend:
         client = self.clients.pop(user_id, None)
 
         if client:
+            try:
+                await client.logout()
+            except MatrixInvalidAccessToken:
+                pass
+
             self.models["accounts"].pop(user_id, None)
             self.models["matching_accounts"].pop(user_id, None)
             self.models[user_id, "uploads"].clear()
@@ -317,8 +322,6 @@ class Backend:
 
             self.models[user_id, "rooms"].clear()
 
-            await client.logout()
-
         await self.saved_accounts.delete(user_id)