"Assign" node can cause a crash when placed in a graph

This may only happen with upgraded projects that went from 4.27 up to 5.0.1

1. Open L.yra
2. Make a new blueprint actor
3. Add the input action binding node "IA_Move"
4. Add a print string to the new node's "Triggered" pin. Additionally, connect "Action Value" to "In String".
5. Enable the saving of generated graphs with "File > Developer > Save intermediate build products"
6. Hit compile
7. Open one of the $INTERMEDIATE$ graphs that appears in the Blueprint window.
8. Copy the "Assign" node out of the generated uber graph
9. Place it on begin play in the event graph, and attach a new float variable to it
10. Place that actor in the level
11. PIE

Result: Crash