Prestashop 1.6 admin page not loading templates, displayAdminCustomers hook error

[David]

I'm using Prestashop 1.6.1.17.

When I go to Customers menu in the back office and I click on "View" for any customer from the list, the page is loaded with unformatted text. Besides, I cannot see any other templates like the header or the footer. After inspecting elements there are no errors in the console, and I don't see anything in the head tag.

However, I see an error in the information at the end of the page (see the picture):

On the other hand, if I click on "Edit" for any customer from the list the page loads correctly.

Finally, after some tests, I could realize that the problem is the hook called "displayAdminCustomers", so I commented out this code until I fix the bug.

    {* display hook specified to this page : AdminCustomers *}
    {*{hook h="displayAdminCustomers" id_customer=$customer->id|intval}*}

Edited March 13, 2018 by David (see edit history)