Get exception when try to clean string as '@'

[doherty88]

Hello, You can use following code to reproduce this exception. it is happend in version 3.0.4. And I also tried with 3.0.3, there was no excepiton. var Filter = require('bad-words'), filter = new Filter();

console.log(filter.clean("@"));

Thanks Deyang

[vdfdev]

Same for: / ! etc

[johnnyapol]

Appears to be a duplicate of #93