百度人脸设备 faceDetect.detect为什么会返回null呢

const detectResult = faceDetect.detect(  
                BDFaceSDKCommon.DetectType.DETECT_VIS,  
                BDFaceSDKCommon.AlignType.BDFACE_ALIGN_TYPE_RGB_ACCURATE,  
                bDFaceImageInstance as BDFaceImageInstance,  
                null,  
                config.bdFaceDetectListConfig  
            )