Avoidance of Closed Universe
I've added a check to jump point exploration to avoid a situation where the last possible exit from known space leads to an existing system.
Normally, when jump point exploration takes place, there is a small chance to link to an existing system. However, for v2.1.1, this check will be skipped if the jump point being explored is the only one in known space that does not have an existing link. This check includes jump points that the race hasn't yet discovered via survey.
Random stars games can be setup with a small number of systems and/or settings that lead to a lot of loops. Therefore, if this situation occurs in a random stars game, the code will make 20 attempts to find a new system before accepting a link to an existing system.
Any new system generated with the last un-linked jump point in known space will have a minimum of two jump points.
These changes should ensure that at least one avenue of exploration will always exist.