for some reasons, the PID was sometimes not inited correctly in Java

for some reasons, the PID was sometimes not inited correctly in Java

It is supposed to be inited during actor creation, but I've seen
during the SUD'17 a machine where it remained at -1. So, if the PID is
negative, java will ask again to the C for a fixup. We could have
fixed the problem, but chasing down JNI issues is really hard.

I prefer to play nasty and safe here. Or let's call it the belt and
brace approach instead.