When the previewed video stops playing (because of the user or because the media...

When the previewed video stops playing (because of the user or because the media playback has ended), show the regular preview only if the preview setting is on.

Summary:
Bug result after test plan :

{F6698812}

Test Plan:
In dolphin with the information panel
Select a video
Play the video
Disable the preview through the context menu (the video stays playing and visible and this will get fixed in a subsequent review)
Stop the video -> the video preview reappears when it should not

Reviewers: elvisangelaccio

Reviewed By: elvisangelaccio

Subscribers: elvisangelaccio, kfm-devel

Tags: #dolphin

Differential Revision: https://phabricator.kde.org/D19843