Handle termination criteria for switching methods

[dilpath]

FAMoS can start with forward, which may return 0 candidates if there are no feasible forward moves. In a normal forward search, this would reasonably end the search. However, since FAMoS can switch, the search should continue, but with a different method. A user observed that FAMoS does not continue, and instead the search is ended unreasonably early.

[dilpath]

Probably fixed by now -- requires testing...