ios系統 swift語言 webrtc開啟鏡頭後將程式移到背景後出錯

請問一下,小弟目前遇到此問題,不知該如何解,問題如下:
在程式內將webrtc的videoSource, capturer, localVideoTrack設定好後,
if self.source == nil {
self.source = self.factory?.videoSource()
}
if self.capturerCtrl == nil {
let capturer = RTCCameraVideoCapturer.init(delegate: self.source!)
self.capturerCtrl = QTMCapturerController.init(WithCapturer: capturer)
}
if self.localVideoTrack == nil {
self.localVideoTrack = self.factory?.videoTrack(with: self.source!, trackId: “rtc_video”)
}
再將localVideoTrack給self.videoSender?.track並開啟鏡頭後
將程式置入背景時會發生crash然後出現此Log,
WebRTC was compiled with optimization - stepping may behave oddly; variables may not be available.
這個問題不知道錯誤點在哪,還請各位大大幫忙謝謝