An unhinged woman stabbed an elderly man in the stomach in an early Friday Queens attack, cops said.  The maniac knifed the 74-year-old victim in the left side of his gut around 12:30 a.m. at 31st Avenue and 94th Street in Jackson Heights, police said.  He was taken to the Elmhurst Hospital Center, where he was listed in stable condition, police said.  The female suspect knifed the 74-year-old victim in the left side of the stomach at 31st Avenue and 94th Street in Jackson Heights, police said. Google Maps The suspect, wearing all black, fled with the knife, walking toward Jackson Mill Road, authorities said.  She had not been caught several hours later.  Police could not immediately confirm whether the two knew each other, or what led to the violence.  The victim went to the Elmhurst Hospital Center in stable condition, police said.…