Sadly, it looks like 4.0.0-beta15 (or slightly earlier) introduced a small regression when it comes to rendering generic arrays: Having something like type: array inside a response or request body specification resulted in a generic template render error.
This patch should solve this by requiring also the items property being filled before iterating over it.
Fix generic error type
Hey, sorry for the slow response. I'll have time this weekend to look at this.
No worries 😃 Thanks for all your work here!