Seen across multiple users. Occurs on the first frame after the blueprint has broken, but before the track tiles are placed.
crash-2019-07-04_13.21.54-client.txt

here is another one at a different location while laying tracks
crash-2019-07-26_11.03.52-client.txt

https://github.com/cam72cam/ImmersiveRailroading/blob/d8062e0f99595a24142dd5c064f0c579f6ce803b/src/main/java/cam72cam/immersiverailroading/tile/TileRailBase.java#L286

here - I think "parent" is null here on laying longer tracks

Minecraft Server Specs:
Xenserver 6.5 running on Dell T610
Model: Intel(R) Xeon(R) CPU X5650 @ 2.67GHz x2
Total memory: 32 Gb ECC RAM DDR3

Minecraft VM:
4 Sockets with 1 Core per socket (configurable in Xen)
Ubuntu 16.04.6 LTS
VM RAM 10 GB

crash-2019-08-11_14.16.48-client.txt
crash-2019-08-11_14.26.07-client.txt
crash-2019-08-11_13.49.44-client.txt
latest.log