Non valid strings generated

Used version:  1.0.2

Example code to reproduce:

```
        SystemPreferenceList out = new SystemPreferenceList();
        Generex generex = new Generex("(^$)|(^[a-zA-Z0-9_-]+(\\.[a-zA-Z0-9_-]+)*$)");
        System.out.println(generex.random());
```

Generated string: ^_XC-_5o_-K-.X.6-0$

This string doesnt match the regex
Regex online to validate:
https://regex101.com/r/XelPbS/1