Emergency stopping Dexter from DDE

[cfry]

If there is a long instruction running,
(such as in calibrate with a slow speed, move_all_joints can
take 5 minutes)
then clicking the stop button sends an "empty instruction queue now (E oplet )
cmd to dexter but that doesn't stop an ongoing instruction.
It may be the case the "E" doesn't empty the queue as it is
intended to.