BuildCraft version: 7.99.16
Forge version: 14.23.4.2705
Link to crash report or log:
crash-2018-06-07_13.35.40-client.txt
crash-2018-06-07_13.35.41-client.txt
crash-2018-06-07_13.37.40-client.txt
Singleplayer or multiplayer: single
Steps to reproduce: break a laser while it is actively working.
Additional information: client crashes, spitting out the first crash log, then a long list of over 100 identical crash logs like the second one, then finally spitting out the third crash log at the end.

It looks like the TESR continues rendering after the block is set to air. I think we just need to add a check to ensure that the laser is actually present before checking to see what side it is facing.