dix/events: reuse grab pointer value

dix/events.c

@@ -1573,7 +1573,7 @@ DeactivatePointerGrab(DeviceIntPtr mouse)
                emulate a ButtonRelease here. So pretend the listener
                already has the end event */
             if (grab->grabtype == CORE || grab->grabtype == XI ||
-                    !xi2mask_isset(mouse->deviceGrab.grab->xi2mask, mouse, XI_TouchBegin)) {
+                    !xi2mask_isset(grab->xi2mask, mouse, XI_TouchBegin)) {
                 mode = XIAcceptTouch;
                 /* NOTE: we set the state here, but
                  * ProcessTouchOwnershipEvent() will still call