Fix MessageVideo, MessageAudio file extension checking bugs

### $file_parts['extensions'] is a typo
$file_parts['extensions']  =>  `$file_parts['extension']`

    //  always is ture when $file_parts['extension'] is `mp4` 
    if ($file_parts['extension'] != 'mp4' || $file_parts['extension'] != 'mov') {

Change to

    $extension        = strtolower(pathinfo($file, PATHINFO_EXTENSION));
    $allowedExtesions = array('mp4', 'mov');
    if (!in_array($extension, $allowedExtesions)) {