This happened to me too: the same BUG() with the same stacktrace, on 4.17-rc2. 
It was when I was away, so maybe it happened when the screen turned off due to
inactivity.  Graphics card is an Radeon RX 550, one monitor connected via HDMI.
 Didn't happen with 4.16.  I did not test 4.17-rc1.