message: fix unitialized field read when no memory is used
diff: @@ -152,7 +152,7 @@ class Memory {
  }
  std::map<smt::expr, AliasSet> ptr_alias; // blockid -> alias
  - unsigned next_nonlocal_bid;
  + unsigned next_nonlocal_bid = 0;
  unsigned nextNonlocalBid();
  static bool observesAddresses();
  