PHP notice is displayed for .ogg file extension on uploader page

After uploading the .ogg mp3 file the php notice is displayed on the uploader page. Below notice is displayed. 

```
Notice: Undefined offset: 0 in /var/www/htdocs/current/wp-content/plugins/transcoder/admin/rt-transcoder-handler.php on line 272
81
```

![image](https://github.com/rtCamp/transcoder/assets/44057535/0e1b06a1-05c7-472a-8d6e-edaff3185bef)
