Trying to access array offset on value of type null (8)

    }
</style>

        <div class="row row-wrapper-center">
            <div class="col-9 blog-detail">
                <?php if($this->getVar("articleDetail")["mId"] > 0 && ( $this->getVar("articleDetail")["mStat"] == 1 || $this->getVar("loginUser")["mId"] > 0 )){ ?>
                <h3 class="article-title"><?php echo $this->getVar("articleDetail")["mTitle"] ?></h3>
                <div class="row article-attrs">
                    <div class="col-6">
                        发表于 <?php echo $this->getVar("articleDetail")["mDatetime"] ?>
                    </div>

tfphp\tfdumpError() in /var/www/html/web-inf/view/tfview/compile/home/blog/detail.html.php line 17
include_once() in /var/www/tfphp/dist/view/tfview.inc.php line 166
tfphp\view\tfview::doLoad() in /var/www/tfphp/dist/view/tfview.inc.php line 195
tfphp\view\tfview::load() in /var/www/tfphp/dist/system/tfpage.inc.php line 23
tfphp\system\tfpage::load() in /var/www/tfphp/dist/tfphp.inc.php line 221
tfphp\tfphp::start() in /var/www/tfphp/dist/tfphp.inc.php line 225
tfphp\tfphp::run() in /var/www/html/index.php line 31
tfproject\index::run() in /var/www/html/index.php line 34