Fixed bug 4011 - Wayland: fix free cursor

Vladimir

Sometimes SDL application crashes on cursor free.

Patch tested under Centos 7 + weston

src/video/wayland/SDL_waylandevents.c

@@ -588,6 +588,7 @@ seat_handle_capabilities(void *data, struct wl_seat *seat,
     } else if (!(caps & WL_SEAT_CAPABILITY_POINTER) && input->pointer) {
         wl_pointer_destroy(input->pointer);
         input->pointer = NULL;
+        input->display->pointer = NULL;
     }
 
     if ((caps & WL_SEAT_CAPABILITY_TOUCH) && !input->touch) {