message: small fix to postgres_query_executor_test
diff: @@ -1522,9 +1522,10 @@ namespace iroha {
  checkSuccessfulResult<TransactionsPageResponse>(
  std::move(query_response),
  [this, size](const auto &tx_page_response) {
  + ASSERT_FALSE(tx_page_response.transactions().empty());
  EXPECT_EQ(tx_page_response.transactions().begin()->hash(),
  this->tx_hashes_.at(0));
  - ASSERT_TRUE(tx_page_response.nextTxHash());
  + EXPECT_TRUE(tx_page_response.nextTxHash());
  this->generalTransactionsPageResponseCheck(tx_page_response, size);
  });
  }
  