Fix Ctrl+Shift and other modifier keys as input-sources switch shortcut
I am not able to use Ctrl+Shift, Control+Alt and other combinations which include only modifier keys to switch input source. My OS is Ubuntu 18.04.1 LTS, gnome-flashback vesion 3.28.0-1ubuntu1.2. I have reported a bug on https://bugs.launchpad.net/ubuntu/+source/gnome-flashback/+bug/1797352
The problem with function gtk_accelerator_valid(keyval, modifiers), which always return False for such combinations. So I`ve just removed this validation. Patch also include fix for modifier release event. add-support-modifiers-only.patch