Falling back from korean dips?

I started korean dips today and could do them reasonably, but was afraid of locking the arms totally and fall back. What to do in case it happens? Just keep gripping the bar and fall in a kind of German hanging position?

If you lock the arms at the top you should be resting for a very quick second at the top of the movement. But yes, if you somehow fall off the back, just try to dismount as safely as possible. Do them with a soft surface under you.