Updater won't work in 12.0 beta 2

[hkistemaker]

Steps to reproduce

1. Update 12.0 beta 2 to beta 3
2. Click Start update button.
3. Nothing happens

Expected behaviour

Web updater checks should run.

Actual behaviour

Nothing, only the Start update button is pressed.

Server configuration

Operating system:
Ubuntu 16.0.4.2
Web server:

Database:
MariaDB 10.1.23
PHP version:
7.0.15
Nextcloud version: (see Nextcloud admin page)
12.0 beta 2
Updated from an older Nextcloud/ownCloud or fresh install:
update from 10 to 11 and then 12

[ChristophWurst]

Duplicate of nextcloud/updater#108