Allow set dump binary path with empty value

[mokhosh]

Currently if no value gets passed to the setDumpBinaryPath because of different environment variables, you get this:

production.ERROR: Too few arguments to function Spatie\DbDumper\DbDumper::setDumpBinaryPath(), 0 passed

But this makes it possible to have a custom path in some environments, and set it back to default which is already an empty string when no parameters are passed.

[freekmurze]

Thanks!