I had the same concern with a pantry door that is hidden behind the slide when closed - slide could catch the door and rip it off while opening. I installed a screen door lock. The lock stays open while we are camping, it doesnt change the door operation at all. Engaging the lock is part of my closing checklist before pulling the slide in so it is latched while traveling and when I am operating the slide. It is on a Keystone Cougar TT. Here is the lock, they are available in different sizes so you could span to the frame.
https://www.amazon.com/Prime-Line-9847-Sliding-Hardened-Diecast/dp/B004AHVA5S/ref=sr_1_6?s=hi&ie=UTF8&qid=1518363597&sr=1-6&keywords=screen+door+lock
Lots of different solutions, this worked for me.
