NOTE: I have been unable to repro this locally, but the crash is because of a null de-reference so we can at least add that to fix up the issue for them.
Result: Crash
Expected: you get the current value of the input action
Note: I have been unable to repro this issue locally.
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-171406 in the post.