getFiniteStrings has a bug when the initial state is an accept state

The following assertion fails. (in scala)
```scala
assert(
    BasicOperations.union(BasicAutomata.makeString(""), BasicAutomata.makeEmpty())
        .getFiniteStrings().asScala == Set("")
)
```

It appears there is a bug in the `getFiniteStrings` function. When:
- initial state is accept state 
- the automata has no transitions

nothing is added to ```strings```.
