Demi Moore decided to sign up for ‘The Substance’ after comparing it to ‘Ghost’. The 60-year-old actress starred in the 1990 supernatural film opposite Patrick Swayze and Whoopi Goldberg, and when she was sent the script for the upcoming movie – in which she stars as an aerobics performer who is fired on her 50th when her boss deems her too old for the job – she decided it could either be “a disaster or somehow work”, just like when she landed the role that made her famous. She told Empire: “Reading ‘Ghost’. ‘This could either be a disaster, or come together and somehow work.’ [‘The Substance’…