Error on creating address

[MaartenPol]

When a customer creates a new address he/she gets an Error 500 message. The address is saved in database though. When you go to /addresses the new address is there, with the country too.
 
When I enable Debug, the message in the attachement is shown

 

My Prestashop version is 1.7.1.2. This webshop is recently updated from 1.3. The error is with my own theme, and with default theme. There are no overrides in classes / controllers whatsoever. I'm on PHP 5.6.31, MySQL 5.5.27
 
What I tried so for:
Recreated the ps_customer, ps_address and ps_address_format tables, and inserted the old data.
Reuploaded the classes folder from PS website download
Caches cleared
 
Any one has a brilliant idea where to look?

Edited July 31, 2017 by MaartenPol (see edit history)

[Scully]

I'd try to add a logger statement in order to figure out which field throws the error. I am guessing the code above runs in a loop for every field.