password: do not abort on trying to remove a user without password account

wcs/qommon/ident/password.ptl

@@ -1574,7 +1574,10 @@ def handle_unused_accounts(publisher):
                 account.store()
 
         if (time.time() - user.last_seen) > 86400*remove_unused_account_delay:
-            account = PasswordAccount.get_on_index(user.id, 'user_id')
+            try:
+                account = PasswordAccount.get_on_index(user.id, 'user_id')
+            except KeyError:
+                continue
             user.remove_self()
             account.remove_self()