Weston fails if there are no input devices

[[0;1;31m●[[0m weston.service - Weston reference Wayland compositor
   Loaded: loaded (/lib/systemd/system/weston.service; disabled; vendor preset: enabled)
   Active: [[0;1;31mfailed[[0m (Result: exit-code) since Mon 2016-12-12 16:17:14 UTC; 20s ago
  Process: 306 ExecStop=/usr/bin/killall -s KILL weston [[0;1;31m(code=exited, status=1/FAILURE)[[0m
  Process: 225 ExecStart=/usr/bin/weston-launch -u root -- --idle-time=4294967 [[0;1;31m(code=exited, status=1/FAILURE)[[0m
 Main PID: 225 (code=exited, status=1/FAILURE)

Dec 12 16:17:10 raspberrypi3 weston-launch[225]: pam_unix(login:session): session opened for user root by (uid=0)
Dec 12 16:17:14 raspberrypi3 weston-launch[225]: failed to restore keyboard mode: Bad file descriptor
Dec 12 16:17:14 raspberrypi3 weston-launch[225]: failed to set KD_TEXT mode on tty: Bad file descriptor
Dec 12 16:17:14 raspberrypi3 weston-launch[225]: could not reset vt handling
Dec 12 16:17:14 raspberrypi3 systemd[1]: [[0;1;39mweston.service: Main process exited, code=exited, status=1/FAILURE[[0m
Dec 12 16:17:14 raspberrypi3 systemd[306]: weston.service: Executing: /usr/bin/killall -s KILL weston
Dec 12 16:17:14 raspberrypi3 killall[306]: killall: weston: no process killed
Dec 12 16:17:14 raspberrypi3 systemd[1]: [[0;1;39mweston.service: Control process exited, code=exited status=1[[0m
Dec 12 16:17:14 raspberrypi3 systemd[1]: [[0;1;39mweston.service: Unit entered failed state.[[0m
Dec 12 16:17:14 raspberrypi3 systemd[1]: [[0;1;39mweston.service: Failed with result 'exit-code'.[[0m