window: Check for NULL surface in keyboard_handle_enter

This can happen if you right-click in weston-terminal a few times very quickly.
The pointer_handle_enter callback already checks for NULL, so let's do that in
keyboard_handle_enter, too.

Signed-off-by: Dima Ryazanov <dima@gmail.com>
Reviewed-by: Daniel Stone <daniels@collabora.com>
1 file changed