input: Handle correctly failure to compile XKB keymaps
We don't have have a keyboard device count ref when we couldn't compile the XKB keymap so avoid tripping an assert when that happens, and avoid sending key events as the weston_keyboard is not created in the same situation.
Fixes: #485 (closed), #402 (closed)
Signed-off-by: Marius Vlad marius.vlad@collabora.com