When it occurs, tape it up or otherwise hold it together as it heals. Looks like it healed up on its own.
Leave more stem above a node when you top and it will more likely avoid this problem, but can still happen. I had a few plants split at top and didn't notice.. they healed on their own. The pressure over time from training can slowly cause it to happen. When you lst, shape the stem before tying it down -- weaken it but not as strenuously as HST. Bend in a few spots to shape it before tying it down.. reduce the constant stress on the node.