Fix initialisation of the first hit error in VeloKalman
Lera (@valukash) pointed me to this commit. The above chance introduces a bug. If the first hit is skipped in the loop over the hits, then the covariance matrix must be initialized with the errors on the position of the first cluster.
Follows this comment by @wouter .
The same applies to ParKalmanVeloOnly
in Allen.
Edited by Andrii Usachov