Prevent an infinite loop when the trimmed text is shorter than the condensed length

When the contents of the element are only text (`clone.html().length == clone.text().length`) and the substring is as long as or longer than the condensed length (`loc >= opts.condensedLength`) and the trimmed body is shorter than the condensed length (`clone.text().length < opts.condensedLength`), then `delta` will be zero and the `do`/`while` loop will be stuck in an infinite loop. Here's an example where this reliably happens:

```html
<div id="demo">
              I wandered around the streets interviewing people and filming the sights on the day of the Royal wedding, I've never seen so many Union Jacks.
              
              Shot at 50fps using a Canon 7D, and because I didn't have my sound device I also used it to record the audio, holding it on the end of the tripod like a microphone.
              
              Music Soda by Cinematic Orchestra 
              
              twitter.com/davedingo
</div>
```

Then run this code:

```javascript
$('#demo').condense({condensedLength: 400});
```