[3.1.0] After adding a Task I see a blank page with OK

[ugo.chirico]

Collabtive Version: 3.1.0
Web browser (+ Version): Google Chrome 61.0.3163.100 and Up / Firefox 56.0

After adding a task in a task list I always got a blank page with OK at the top left and nothing more.

Steps to reproduce:

open a task list
add a task
edit the task form
click on "add" button

[Philipp]

I will investigate for 3.2