Pull workqueue fix from Tejun Heo:
 "Another fix for a really old bug.

  It only affects drain_workqueue() which isn't used often and even then
  triggers only during a pretty small race window, so it isn't too
  surprising that it stayed hidden for so long.

  The fix is straight-forward and low-risk. Kudos to Li Bin for
  reporting and fixing the bug"

* 'for-4.14-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq:
  workqueue: Fix NULL pointer dereference