Masquerade Menu Access problem

Hi.
After an upgrade from D6 to D7 I'm having a strange problem.
Log reports :
Trying to get property of non-object in masquerade_menu_access(); For every single page.

So far every functionnality of the module just appear to work nicely.
I tryed to debug a bit the problem and found that an uid that is not existing anymore in the system (109 - deletted user) is being passed to the fonction masquerade_menu_access($type, $uid = NULL).
so that masquerade_menu_access('switch', 109);

As consequence, when $account = user_load($uid); comes
$account stays undefined and then when $account->uid; arrives
then the bug occurs.

For sure adding the line :
if (!$account){
return FALSE;
}

fixed the problem... But I didn't managed to find why this wrong uid was passed to the function ?
And why this function is called at every single page calls. Isn't it supposed to work only at user switch ?
Any hints are greatly appreciated.

Thanks.