It appears Unity8 crashed (in Mir) when changing display configuration (which is probably the setting of the display power mode to standby/suspend/off):

[2017-01-13 10:28:09.313008] mirserver: New display configuration:
[2017-01-13 10:28:09.313637] mirserver:   Output 37: eDP connected, used
[2017-01-13 10:28:09.313807] mirserver:       Physical size 11,6" 260x140mm
[2017-01-13 10:28:09.313949] mirserver:       Current mode 1366x768 60,08Hz
[2017-01-13 10:28:09.314087] mirserver:       Preferred mode 1366x768 60,08Hz
[2017-01-13 10:28:09.314253] mirserver:       Logical position +0+0
[2017-01-13 10:28:09.314387] mirserver:   Output 34: VGA disconnected
[2017-01-13 10:28:09.314521] mirserver:   Output 46: DisplayPort disconnected
[2017-01-13 10:28:09.314654] mirserver:   Output 48: HDMI-A disconnected
[2017-01-13:10:28:09.314] qtmir.screens: QtCompositor::stop
[2017-01-13:10:28:09.316] qtmir.screens: ScreensModel::onCompositorStopping
[2017-01-13:10:28:09.316] qtmir.screens: ScreenWindow::setExposed 0x1467100 false 0x7f56482557b0
[2017-01-13:10:28:09.339] qtmir.screens: ScreensModel::update
[2017-01-13:10:28:09.340] qtmir.screens: Screen::setMirDisplayBuffer Screen(0x7f56482557a0) 0x7f5648159240 0x7f5648159390
[2017-01-13:10:28:09.340] qtmir.screens: =======================================
[2017-01-13:10:28:09.340] qtmir.screens: Screen(0x7f56482557a0) - id: 37 geometry: QRect(0,0 1366x768) window: 0x1467100 type: "EDP" scale: 1
[2017-01-13:10:28:09.340] qtmir.screens: =======================================
[2017-01-13:10:28:09.350] qtmir.screens: QtCompositor::start
[2017-01-13:10:28:09.350] qtmir.screens: ScreensModel::onCompositorStarting
[2017-01-13:10:28:09.350] qtmir.screens: ScreensModel::update
[2017-01-13:10:28:09.350] qtmir.screens: =======================================
[2017-01-13:10:28:09.350] qtmir.screens: Screen(0x7f56482557a0) - id: 37 geometry: QRect(0,0 1366x768) window: 0x1467100 type: "EDP" scale: 1
[2017-01-13:10:28:09.350] qtmir.screens: =======================================
[2017-01-13:10:28:09.351] qtmir.screens: ScreenWindow::setExposed 0x1467100 true 0x7f56482557b0
terminate called after throwing an instance of 'boost::exception_detail::clone_impl<boost::exception_detail::error_info_injector<std::system_error> >'
  what():  Nested Mir Display Error: Failed to update EGL surface: EGL_BAD_CONTEXT (0x3006)
[2017-01-13:10:28:11.613] qtmir.screens: ScreensModel::ScreensModel
[2017-01-13 10:28:11.633539] mirplatform: Found graphics driver: mir:mesa-kms (version 0.25.0)
[2017-01-13 10:28:11.634065] mirplatform: Found graphics driver: mir:mesa-x11 (version 0.25.0)
[2017-01-13 10:28:11.636461] mirserver: Starting
xkbcommon: ERROR: couldn't find a Compose file for locale "fr_FR.UTF-8"
xkbcommon: ERROR: couldn't find a Compose file for locale "fr_FR.UTF-8"
[2017-01-13 10:28:11.669388] mirserver: Using nested cursor
[2017-01-13 10:28:11.672854] mirserver: Initial display configuration:
[2017-01-13 10:28:11.673466] mirserver:   Output 37: eDP connected, used
[2017-01-13 10:28:11.673856] mirserver:       Physical size 11,6" 260x140mm
[2017-01-13 10:28:11.674229] mirserver:       Current mode 1366x768 60,08Hz
[2017-01-13 10:28:11.674599] mirserver:       Preferred mode 1366x768 60,08Hz
[2017-01-13 10:28:11.674965] mirserver:       Logical position +0+0
[2017-01-13 10:28:11.675337] mirserver:   Output 34: VGA disconnected
[2017-01-13 10:28:11.675705] mirserver:   Output 46: DisplayPort disconnected
[2017-01-13 10:28:11.676162] mirserver:   Output 48: HDMI-A disconnected