It is the kind of crime many small business people fear, and hope they never encounter. As he locked the door to Yang's Market on Wednesday January 18, Yong Yang had cash in his pocket to buy wholesale produce the next morning at the produce depot in Philadelphia. As Yang climbed into his delivery truck, he was jumped by two robbers  who dragged him out of the driver's side door. The Crime Easttown Police Chief David Obzud tells Patch two teens, 18-year-old Octavio Sandoval, and a 17-year-old accomplice "displayed a knife" and punched Yang in the face. It was a devastating blow that shattered…