Information Panel: show the phonon when we can use phonon

Summary: Similar to D29158

Test Plan:
Select a video file
Type CTRL + F and some text
Hit ALt + left or previous button

Before:
The video controls are not visible for selected video file

After:
Video controls are visible again.

Reviewers: ngraham, elvisangelaccio, #dolphin

Reviewed By: ngraham, #dolphin

Subscribers: kfm-devel

Tags: #dolphin

Differential Revision: https://phabricator.kde.org/D29160