While in a 17w15a world and 1.11.2 world opened in 17w15a i built a Redstone torch tower.
When i placed a Redstone torch *on the bottom of a solid block with air and solid block under; the whole game crashed; didn't save; and returned the launcher's game crash window. I have tested the crash with *Regular torches and they crash in the same placement too.

I tested the same placement in 1.11.2 version and it was valid in that version.
Attached is a screen shot of before reproducing the crash. Placing the Redstone torch from the bottom of the dirt block onto the one below it causes the crash. The text file is the launcher readout from the crash.