Fix RottenTomatoes filter

As discussed in http://flexget.com/ticket/2574, looks like if there are no reject options in the config then the filter accepts all the movies it should ignore.

There's a test in my last comment in the ticket. The results after this fix:
```
pydev debugger: starting
2014-04-29 16:39 VERBOSE  details       rtf             Produced 3 entries.
2014-04-29 16:39 VERBOSE  task          rtf             ACCEPTED: `inception.1080p.lol` by rottentomatoes plugin because accept_actors Leonardo DiCaprio
2014-04-29 16:39 VERBOSE  task          rtf             ACCEPTED: `inglorious.bastards.720p.lol` by rottentomatoes plugin because accept_actors Christoph Waltz
2014-04-29 16:39 VERBOSE  details       rtf             Summary - Accepted: 2 (Rejected: 0 Undecided: 1 Failed: 0)
2014-04-29 16:39 WARNING  task          rtf             Task doesn't have any output plugins, you should add (at least) one!
```