client: holding freeze a frame instead of showing black.
Issue generated from Tuleap's migration script. Originally submitted by: Nicolas Jager (nicolasjager-sfl)
if during a call, I click on hold, I get a frame freezed rendered. the videoWidget isn't updated properly to black.
moving the cursor on some buttons in the video-bar lead to a black square around the buttons.
pressing a key, moving the cursor out the window triggers the update.