fix for failed download with no subtitles when requested

At the moment if video doesn't have subtitles but they were requested by the user `youtube-dl` fails with ... 

```bash
events.js:72
        throw er; // Unhandled 'error' event
              ^
Error: : video doesn't have subtitles

    at /test/youtube-dl/lib/youtube-dl.js:122:23
    at ChildProcess.exithandler (child_process.js:645:7)
    at ChildProcess.emit (events.js:98:17)
    at maybeClose (child_process.js:755:16)
    at Process.ChildProcess._handle.onexit (child_process.js:822:5)
```

... this fix catches and removes possible options passed by the user and tries once to download video only without the subtitles.
why not traverse the list of args backwards so the item doesn't have to be searched for again?