That is the best thing to do, there is a kit you can order and put onto the heater or you can use a piece of copper wire. Hang it from the defrost heater and into the drain about 1/4 inch. What that will do is keep the drain and the water warm longer so it does not freeze so fast. That is one method. The link is below.
The second thing you can do is replace the defrost thermostat that is clipped to the top of the coils. It is a disk shaped object with 2 wires coming from it. Replace that with a warmer thermostat and that will help. Most all of those will have a temperature on them and if you will take it to an appliance parts store and explain that you would like one that is a few degrees warmer that will help 4 to 10 degrees can make a big difference during the defrost cycle. That will keep the heater on a little longer and should stop the freezing.Please ask if you have questions, if not then please leave a rating for me.Thank you,Barry
In my past life I was an appliance repairman for Public Service Co of Colorado. I have repaired many GE and Hotpoint refrigerators with a similar fix.
Thanks for your help.