DebugKit Panel not showing (3.22.4) and error thrown in console

[nilsonpena]

Everything works in 3.22.3 but when upgrades to 3.22.4 the following error appears in console and the panel get hidden

Ubuntu 20.04
PHP 7.4.3
Cakephp 3.9.6
Chrome 88.0.4324.146 (Versão oficial) 64 bits

Thanks in advance

<pre class="cake-error"><a href="javascript:void(0);" onclick="document.getElementById('cakeErr601864f51628a-trace').style.display = (document.getElementById('cakeErr601864f51628a-trace').style.display == 'none' ? '' : 'none');"><b>Notice</b> (8)</a>: Undefined index: className [<b>ROOT/vendor/cakephp/debug_kit/src/Panel/MailPanel.php</b>, line <b>55</b>]<div id="cakeErr601864f51628a-trace" class="cake-stack-trace" style="display: none;"><a href="javascript:void(0);" onclick="document.getElementById('cakeErr601864f51628a-code').style.display = (document.getElementById('cakeErr601864f51628a-code').style.display == 'none' ? '' : 'none')">Code</a> <a href="javascript:void(0);" onclick="document.getElementById('cakeErr601864f51628a-context').style.display = (document.getElementById('cakeErr601864f51628a-context').style.display == 'none' ? '' : 'none')">Context</a><pre id="cakeErr601864f51628a-code" class="cake-code-dump" style="display: none;"><code><span style="color: #000000"><span style="color: #0000BB"></span></span></code>
<span class="code-highlight"><code><span style="color: #000000"><span style="color: #0000BB">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;$className&nbsp;</span><span style="color: #007700">=&nbsp;</span><span style="color: #0000BB">App</span><span style="color: #007700">::</span><span style="color: #0000BB">className</span><span style="color: #007700">(</span><span style="color: #0000BB">$transport</span><span style="color: #007700">[</span><span style="color: #DD0000">'className'</span><span style="color: #007700">],&nbsp;</span><span style="color: #DD0000">'Mailer/Transport'</span><span style="color: #007700">,&nbsp;</span><span style="color: #DD0000">'Transport'</span><span style="color: #007700">);</span></span></code></span>
<code><span style="color: #000000"><span style="color: #0000BB"></span></span></code></pre><pre id="cakeErr601864f51628a-context" class="cake-context" style="display: none;">$reflection = object(ReflectionClass) {
	name =&gt; &#039;Cake\Mailer\TransportFactory&#039;
}
$property = object(ReflectionProperty) {
	name =&gt; &#039;_config&#039;
	class =&gt; &#039;Cake\Mailer\TransportFactory&#039;
}
$configs = [
	&#039;default&#039; =&gt; [
		&#039;transport&#039; =&gt; &#039;default&#039;,
		&#039;from&#039; =&gt; &#039;you@localhost&#039;
	]
]
$log = object(ArrayObject) {
	
}
$transport = [
	&#039;transport&#039; =&gt; &#039;default&#039;,
	&#039;from&#039; =&gt; &#039;you@localhost&#039;
]
$name = &#039;default&#039;</pre><pre class="stack-trace">DebugKit\Panel\MailPanel::initialize() - ROOT/vendor/cakephp/debug_kit/src/Panel/MailPanel.php, line 55
DebugKit\ToolbarService::initializePanels() - ROOT/vendor/cakephp/debug_kit/src/ToolbarService.php, line 196
DebugKit\Middleware\DebugKitMiddleware::__invoke() - ROOT/vendor/cakephp/debug_kit/src/Middleware/DebugKitMiddleware.php, line 52
Cake\Http\Runner::__invoke() - CORE/src/Http/Runner.php, line 65
Cake\Http\Runner::run() - CORE/src/Http/Runner.php, line 51
Cake\Http\Server::run() - CORE/src/Http/Server.php, line 97
[main] - ROOT/webroot/index.php, line 37</pre></div></pre>

[othercorey]

What version of cakephp and php are you using?