I found that problem when the stream is offline because of the empty data in api of mixer. I will fix it in the next version or you can fix it by editting file
\applications\videobox\Application.php
Find
$data = $this->mixerData($request[0]);
Replace by
$data = $this->mixerData($request[0], $name);
Find
public function mixerData($sdata)
Replace by
public function mixerData($sdata, $name)
Find
'media' => "//mixer.com/embed/player/". $sdata['id'],
'chat' => "//mixer.com/embed/chat/". $sdata['id'],
Replace by
'media' => "//mixer.com/embed/player/". $name,
'chat' => "//mixer.com/embed/chat/". $name,
Save