
Similar to 7c4f6cc145daf66cd9624f1e70dd5278241f5858, if we don't have a background image from the desktop-shell client or the touch point for some other reason doesn't hit a surface we trigger a segfault as we try to deref the seat->touch->focus NULL pointer. For touch, another problem could be fudgey calibration that ends up giving touch coordinates outside the output space. https://bugs.freedesktop.org/show_bug.cgi?id=72839