message: shufflevector: fix crash with full undef mask
diff: @@ -2089,6 +2089,9 @@ StateValue ShuffleVector::toSMT(State &s) const {
  auto mty = mask->getType().getAsAggregateType();
  vector<StateValue> vals;
  + if (dynamic_cast<UndefValue*>(mask))
  + return UndefValue(getType()).toSMT(s);
  +
  auto &vect1 = s[*v1];
  auto &vect2 = s[*v2];
  auto &mask_vector = static_cast<AggregateConst*>(mask)->getVals();
  