Split or broken stems are pretty common for a number of reason in smaller plants, if you have grown for a numbers years it is hard not to encounter this from time to time. Just my two cents from what I have done in the past, I prop the plant up straight to bring the split together as much as possible. Then with sewing thread and some thin padding (first aid gauze for example) wrap the split with the cloth or gauze and gently tie the split together. Usually within a few days the split is healed although you will have a knot at the split and it will tend to be weaker than the rest of the plant she will survive. Keep the pressure off the where the injury occurred with small stakes or some other way to help support it and you should have a viable plant through harvest. I hope that this helps and good luck.