Slide navigator: focus on the first slide

[ferserc1]

When opening the timeline pop up of the slide navigator for the first time, the focus is correctly placed on the first slide, but the rest of the times it is opened it is not.

1 - open paellaplayer.upv.es
2 - play the video
3 - go to slide navigation plugin using the tab key
4 - press enter. The first slide is focused
5 - press esc
6 - repeat the steps 3 and 4. The focus is lost