Comment 1 for bug 1498550

This is possibly a dup of https://bugs.launchpad.net/mir/+bug/1474891 but with mir 0.15.

The fix in lp:1474891 is not sufficient as the android platform may be already in the middle of waiting for HWC->set call with a list that includes the external display at the time the external display is unplugged. In which case, set can return -1, but before HWC sends the hotplug event so the exception is thrown.