This is a common crash affecting users in 4.15 and 4.16.
Place a Make Array node
Connect to a Length node
Double click the connection between them to create 3 reroute nodes
Select the last 2 reroute nodes and collapse to macro
Connect the output pin of the macro to the remaining reroute node
Expand the macro
There's no existing public thread on this issue, so head over toAnswerHub just mention UE-47257 in the post.