add missing semicolon

fix.

```
$ grunt build
Loading "clean.js" tasks...ERROR
>> TypeError: Object #<Object> has no method 'registerHelper'

Running "jshint:src" (jshint) task
Linting backbone.stickit.js...ERROR
[L454:C47] Missing semicolon.
        addSelectOptions(["__default__"], $el) 

Warning: Task "jshint:src" failed. Use --force to continue.

Aborted due to warnings.
```