#292 S5: left/right key after left mouse click does nothing

[Christian Weiske]

The S5 slideshow mode offers key navigation.

When left-clicking a slide, I'm going to the next slide. Pressing the "left arrow" key does nothing. Only a second press on "left arrow" actually goes to the previous slide.

After that, it's all fine and key presses work - until I left-click a slide again.

Same with the right key, which should go to the next slide.

"function go()" sets number to 0, so it seems to be intented - but I don't know why.