patch tau filters for decay-less Sherpa status code 20 taus
New Sherpa 2.2.11 have sometimes particles with status code 20 that do not decay. our tau-filters assume that end_vertex() does not return a null pointer and crash
New Sherpa 2.2.11 have sometimes particles with status code 20 that do not decay. our tau-filters assume that end_vertex() does not return a null pointer and crash