Access Violation in CvEM::getCovs function

I am using cvEm for Gaussian Mixture modeling on a 2D data. After calling the train function it returns True (signing a successful training) and also classification results (having different clusters in different colors) seem reasonable, but I get an access violation error while getting co-variance matrices of clusters!

Following is the related lines of code:

    CvEMParams params;
    params.covs      = NULL;
    params.means     = NULL;
    params.weights   = NULL;
    params.probs     = NULL;
    params.nclusters = NrGMMComponents;
    params.cov_mat_type       = CvEM::COV_MAT_GENERIC; // DIAGONAL, GENERIC, SPHERICAL
    params.start_step         = CvEM::START_AUTO_STEP;
    params.term_crit.max_iter = 300;
    params.term_crit.epsilon  = 0.001;
    params.term_crit.type     = CV_TERMCRIT_ITER|CV_TERMCRIT_EPS;
    //params.term_crit.type     = CV_TERMCRIT_ITER;

    // 2.2 Estimate GMM params for all <NrGMMComponents> Gaussian Mixture Components
    
    CvEM em_model;
    bool result = em_model.train( samples, Mat(), params, &labels);
    vector<cv::Mat> covs;
    em_model.getCovs(covs);  ////////////Access Violation here! :(

I found another member function in CvEm called get_covs() and it worked! But I still do not know what's wrong with the getCov() function.