message: state: ignore jumps with false path condition
  this fixes crashes in startBB due to disjointexpr const folding
diff: @@ -140,6 +140,9 @@ bool State::startBB(const BasicBlock &bb) {
  }
  void State::addJump(const BasicBlock &dst0, expr &&cond) {
  + if (cond.isFalse())
  + return;
  +
  auto dst = &dst0;
  if (seen_bbs.count(dst)) {
  dst = &f.getBB("#sink");
  