离开DispatchGroup会导致我的代码崩溃

我有以下功能,但它总是在 dispatchGroup.leave()语句,我不明白为什么。根据我在网上找到的信息,每个dispatchgroup.leave()都必须与dispatchgroup.enter()相关联,我相信我的函数就是这样。

self.kycrecords只包含1个元素(暂时)。

 @IBAction func checkCustomerList(_ sender: Any) {
        let dispatchGroup = DispatchGroup()

        for kycRecord in self.kycRecords {
            dispatchGroup.enter()
            ApiManager.sharedInstance.postUserToArtemis(kycRecord) {(response, error) in
                dispatchGroup.leave()
                if error != nil {
                    kycRecord.kycStatus = "failed"
                } else {
                    if response == true {
                        kycRecord.kycStatus = "passed"
                    } else {
                        kycRecord.kycStatus = "failed"
                    }
                }
            }
        }

        dispatchGroup.notify(queue: DispatchQueue.main, execute: {
            print("done")
            self.writeOutput()
        })
    }

它会崩溃并显示消息:

线程1:exc_bad_指令(代码=exc_i386_invop,子代码=0x0)