Fullscreen mode disabled after Scan topic dialog

[allgood]

When "scan topic" feature enabled ( commit 554b25e by @thrillfall ), when the dialog asking for the topic string is dismissed, screen mode must get back to full screen.

Steps to reproduce

Set "custom scan topic" on settings page, scan a document, fill a topic string or skip it

Expected behaviour

Screen should get back to fullscreen mode

Actual behaviour

Screen shows header and action buttons over the shutter button