In 'toDimacs()', handle case where solver is in a contradictory state.
In 'toDimacs()', handle case where solver is in a contradictory state.

robertsami/minisat,niklasso/minisat,jamesbornholt/minisat,mabdula/minisat,mabdula/minisat,mabdula/minisat,meteor/minisat,jamesbornholt/minisat,niklasso/minisat,meteor/minisat,meteor/minisat,robertsami/minisat,meteor/minisat