Martin Short emotionally addressed the sudden death of his daughter, Katherine. “It’s been a nightmare for the family,” the “Only Murders in the Building” star told “CBS Sunday Morning.” “But the understanding [is] that mental health and cancer, like my wife’s, are both diseases, and sometimes with diseases they are terminal,” he added, referring to his late wife, Nancy Dolman, who died in 2010. Martin Short has broken his silence on the death of his daughter, Katherine, pictured here with him at the 2011 Vanity Fair Oscars Party. FilmMagic “It’s been a nightmare for the family,” the “Only Murders in the Building” star (seen here in 2006) told “CBS Sunday Morning.” WireImage “And my daughter fought for a long time with extreme mental health, borderline personality disorder, other things, and did the best she couldn’t until she couldn’t,” Short, 76, continued. Katherine tragically died at the age of 42 on Feb. 23.…