As others have said, the risk is very small, and would be unlikely to happen accidentally. Yet, here are some tips/precautions to add to the ones above.
First, avoid sitting on top of the railings. I know that might sound silly, yet a friend of mine caught her teenaged son doing just that when hanging out with friends and there weren't enough seats for all of them.
When my son was very little, we made it a rule that he had to hold my hand or my husband's hand whenever we were on deck. (Overprotective mom here.) Even as he got older, he continued to do so on his own.
Another tip if you are very concerned is to move the balcony furniture away from the railing.