message: return error instead of throw exception when code not exists
diff: @@ -126,18 +126,34 @@ bool is_code_activated( uint64_t account ) {
  }
  const char* get_code( uint64_t receiver, size_t* size ) {
  + if (!db_api::get().is_account(receiver)) {
  + *size = 0;
  + return nullptr;
  + }
  + try {
  const shared_string& src = db_api::get().get_code(receiver);
  *size = src.size();
  return src.data();
  + } catch (...) {
  + *size = 0;
  + return nullptr;
  + }
  }
  int get_code_id( uint64_t account, char* code_id, size_t size ) {
  + if (!db_api::get().is_account(account)) {
  + return 0;
  + }
  + try {
  digest_type id = db_api::get().get_code_id(account);
  if (size != sizeof(id)) {
  return 0;
  }
  memcpy(code_id, id._hash, size);
  return 1;
  + } catch (...) {
  + return 0;
  + }
  }
  int get_code_type( uint64_t account) {
  