A homeless man has been charged with indecent assault and battery of another man in the Harvard Square train station, according to a statement Saturday from MBTA Transit Police. At about 8 p.m. Friday, officers responded to a call from an MBTA employee at the station. The employee said Thomas Dabrikas, 60, had indecently assaulted an 18-year-old autistic man, according to the statement. Dabrikas, a previous Level 3 sex offender, was arrested by Transit Police and charged, according to the statement. He was scheduled to be arraigned Monday in Cambridge District Court.