Don't call XInput2 multitouch APIs if they aren't supported.
I think it fixes this:
http://forums.libsdl.org/viewtopic.php?t=8324&sid=ae797309f9e2084cadc1b6a7615bd0e4
--- a/src/video/x11/SDL_x11xinput2.c Mon Sep 17 19:20:47 2012 -0400
+++ b/src/video/x11/SDL_x11xinput2.c Mon Sep 17 19:25:42 2012 -0400
@@ -220,6 +220,10 @@
void
X11_Xinput2SelectTouch(_THIS, SDL_Window *window) {
#if SDL_VIDEO_DRIVER_X11_XINPUT2_SUPPORTS_MULTITOUCH
+ if (!X11_Xinput2IsMultitouchSupported()) {
+ return;
+ }
+
SDL_VideoData *data = (SDL_VideoData *) _this->driverdata;
XIEventMask eventmask;
unsigned char mask[3] = { 0,0,0 };