bugfix: fix coredump issue when future_execute() return network error

[rayhuang90]

bugfix: 修复future_execute()错误时，ExecutionResponse.spaceName == nullptr，直接解引用导致的coredump问题
bugfix: fix coredump issue when future_execute() return network error. In such case, ExecutionResponse.spaceName == nullptr。There is segment fault at SessionPool.cpp@line45 and line65。

What type of PR is this?

• bug
• feature
• enhancement

What problem(s) does this PR solve?

Issue(s) number:

Description:

segement fault：

full log：
coredump.log
source code:

ExecutionResponse SessionPool::execute(const std::string &stmt) {
  auto result = getIdleSession();
  if (result.second) {
    auto resp = result.first.execute(stmt);
    if (*resp.spaceName != config_.spaceName_) {    // line45
      // switch to origin space
      result.first.execute("USE " + config_.spaceName_);
    }
    giveBack(std::move(result.first));
    return resp;
  }
...
}

根因 / root cause
Connection.cpp @ line145

ExecutionResponse Connection::execute(int64_t sessionId, const std::string &stmt) {
  ExecutionResponse resp;
  try {
    resp = client_->future_execute(sessionId, stmt).get();
  } catch (const std::exception &ex) {
    resp = ExecutionResponse{
        ErrorCode::E_RPC_FAILURE, 0, nullptr, nullptr, std::make_unique<std::string>(ex.what())};
  }
  return resp;
}

How do you solve it?

增加 spaceName 非空判断，不无脑解引用
check ExecutionResponse.spaceName is nullptr before compared with config_.spaceName_

Special notes for your reviewer, ex. impact of this fix, design document, etc:

[CLAassistant]

All committers have signed the CLA.

[rayhuang90]

@yixinglu
这些代码检查流水线失败了，帮忙看一下？我预期我修改的代码，毕竟才加了2个判断语句，不会触发这些流水线告警才对。
hi, please check the code merge request pipeline error. There are only two line of code modification. No warning or pipeline error is expected. Please let me know if i can be of any help.

[yixinglu]

@yixinglu 这些代码检查流水线失败了，帮忙看一下？我预期我修改的代码，毕竟才加了2个判断语句，不会触发这些流水线告警才对。 hi, please check the code merge request pipeline error. There are only two line of code modification. No warning or pipeline error is expected. Please let me know if i can be of any help.

don't worry about these failures which will be fixed later, thanks for your contribution! cc @Shylock-Hg

[Shylock-Hg]

resp.spaceName == nullptr || *resp.spaceName != config_.spaceName_

[songqing]

@Shylock-Hg @rayhuang90 We have met the same problem, could you modify and merge this PR?