public @DrawableRes int getMediaUnCheckedRes() {
        return mMediaUnCheckedRes;
    }
get the media unchecked drawable resource by {@link BoxingConfig#withMediaUncheckedRes(int)} (int)}.
@return >0, set a valid drawable resource; otherwise without a placeholder.
boxing/src/main/java/com/bilibili/boxing/model/config/BoxingConfig.java