Description of problem:

ERROR:gpm-kbd-backlight.c:329:gpm_kbd_backlight_on_dbus_signal: code should not be reached
[1]+  Aborted                 (core dumped) mate-power-manager

Aug 10 14:31:08 laptop systemd-coredump: Process 5757 (mate-power-mana) of user 1000 dumped core.#12#012Stack trace of thread 5757:#12
#0 0x00007f4681c8d66b raise (libc.so.6)#12
#1 0x00007f4681c8f470 abort (libc.so.6)#12
#2 0x00007f46825cd70d g_assertion_message (libglib-2.0.so.0)#12
#3 0x00007f46825cd79a g_assertion_message_expr (libglib-2.0.so.0)#12
#4 0x00005625307f7203 gpm_kbd_backlight_on_dbus_signal (mate-power-manager)#12
#5 0x00007f467cd70bde ffi_call_unix64 (libffi.so.6)#12
#6 0x00007f467cd7054f ffi_call (libffi.so.6)#12
#7 0x00007f468287fb09 g_cclosure_marshal_generic (libgobject-2.0.so.0)#12
#8 0x00007f468287f30d g_closure_invoke (libgobject-2.0.so.0)#12
#9 0x00007f468289198e signal_emit_unlocked_R (libgobject-2.0.so.0)#12
#10 0x00007f468289a1a5 g_signal_emit_valist (libgobject-2.0.so.0)#12
#11 0x00007f468289ab0f g_signal_emit (libgobject-2.0.so.0)#12
#12 0x00007f4682db11bc on_signal_received (libgio-2.0.so.0)#12
#13 0x00007f4682da0a64 emit_signal_instance_in_idle_cb (libgio-2.0.so.0)#12
#14 0x00007f46825a3c27 g_idle_dispatch (libglib-2.0.so.0)#12



Version-Release number of selected component (if applicable):
upower-0.99.5-1.fc26.x86_64
mate-power-manager-1.18.0-1.fc26.x86_64


How reproducible:
Always. It crashes with all notebooks/laptops with keyboard backlights.

Steps to Reproduce:
1. Start using Mate desktop. mate-power-manager applet immediately crashes.


Actual results:
mate-power-manager crashes quickly after it is started. 100% reproducible.

Expected results:
mate-power-manager shouldn't crash.

Additional info:

Upstream bugs:
https://github.com/mate-desktop/mate-power-manager/issues/225
https://github.com/mate-desktop/mate-power-manager/issues/226

Downgrading upower to version 0.99.4 should provice a workaround for the mate-power-manager bug.