Fix #1342 (regression from #1319)

src/lv_core/lv_obj.c

@@ -125,7 +125,9 @@ void lv_init(void)
 void lv_deinit(void)
 {
     lv_gc_clear_roots();
+#if LV_USE_LOG
     lv_log_register_print_cb(NULL);
+#endif
     lv_disp_set_default(NULL);
     lv_mem_deinit();
     lv_initialized = false;