opencv exception: (u->refcount == 0 && umat dellocation error....)

cv::Mat mat(4,4,CV_8U);

1.

cv::UMat umat = mat.getumat(cv::access_fast);

cv::resize(umat, umat, cv::Size(2,2));

2.

cv::UMat umat; mat.copyTo(umat);

cv::resize(umat, umat, cv::Size(2,2));

Both of these methods will cause umat destructor to report an error, can you tell me why？？

Is the resize function not allowed to use the same input and output in this way?