Crash when portal has no reference after copy/paste inside a function

Steps:

Designer 13.1.1 is crashing in the following scenario:

- inside pixel processor, use a portal structure (data going into a portal output then a portal input)

- create a package function, copy subgraph containing the portal output into that function: the portal dot node will loose its source reference inside the function (which is normal)

- make the data flow pass trough the function and the unreferenced portal.

Expected result: Designer would report an error (at least into the console) and not crash

Actual result: Designer crashes

This scenario can happen when copy/pasting code from one place to another, if portals are involved and we forget to re-source them. This is how it happened to me. I have a sample graph demonstrating the problem if needed, but cannot attach it here.