message: Use HandleMissingData also in CheckSchnorrSignature
diff: @@ -1719,7 +1719,7 @@ bool GenericTransactionSignatureChecker<T>::CheckSchnorrSignature(Span<const uns
  if (hashtype == SIGHASH_DEFAULT) return set_error(serror, SCRIPT_ERR_SCHNORR_SIG_HASHTYPE);
  }
  uint256 sighash;
  - assert(this->txdata);
  + if (!this->txdata) return HandleMissingData(m_mdb);
  if (!SignatureHashSchnorr(sighash, execdata, *txTo, nIn, hashtype, sigversion, *this->txdata, m_mdb)) {
  return set_error(serror, SCRIPT_ERR_SCHNORR_SIG_HASHTYPE);
  }
  