SDL_x11events.c: fix build if Xinput2 is not available after 3dfc3b4c8

src/video/x11/SDL_x11events.c

@@ -2036,7 +2036,9 @@ void X11_PumpEvents(SDL_VideoDevice *_this)
     }
 
     if (data->xinput_hierarchy_changed) {
+#ifdef SDL_VIDEO_DRIVER_X11_XINPUT2
         X11_InitPen(_this);
+#endif
         X11_Xinput2UpdateDevices(_this, SDL_FALSE);
         data->xinput_hierarchy_changed = SDL_FALSE;
     }