Bug in admin panel when editting the address of a registered customer while a guest account with the same email exists (ver. 1.7.6.x)

[AndiBalou]

Greetings to all,

I've run into a bug in the administration panel, while editting an address of a registered customer. The customer had already placed an order before using the guest checkout, so his email was already used in an address to connect the address to a "Guest" user group account. After that, he placed an order by using the same e-mail, only this time, he placed a password as well and so registered under the "Customer" user group. When, I tried to change his phone of the address connected to the CUSTOMER ACCOUNT via the admin address form (http://prntscr.com/vy7idw) and saved, the address disappeared from the CUSTOMER ACCOUNT completely (http://prntscr.com/vy7jtu) and it got assigned to the GUEST ACCOUNT. When I tried to create a new one from the admin panel of the CUSTOMER ACCOUNT, it got assigned to the GUEST ACCOUNT as well. Creating or updating an address from the front-office of the site it saves it at the correct account.

I believe that during save and form submission of the admin address form, the script searches the database for the email and not the id of the account that needs to have the address assigned, so because the GUEST ACCOUNT appears first in the database, it gets the address assigned there. I've already tested it in to two different eshops (different templates - ver. 1.7.6.3) and one ver. 1.7.6.8. I also tested it in a 1.7.7.0 RC and there, it works as it should. I need a solution because updating the e-shops is not an option at the current time. The file that I think causes the bug or at least part of the problem is AdminAddressesController.php inside /controllers/admin

Thanks in advance.