I run the stateestimation node in tum_ardrone package and when I try to initialize PTAM I got the error said

/tum_ardrone/src/stateestimation/PTAM/MEstimator.h:79: static double Tukey::FindSigmaSquared(std::vector&): Assertion `vdErrorSquared.size() > 0' failed. Aborted (core dumped)