ARLINGTON -- Niki Jackson might be dead if an unknown passerby had not yelled a warning at her about 7 p.m. Wednesday at Green Oaks Boulevard and Collins Street.The 1996 Toyota Camry she had bought just six days earlier had died.It stopped running. The lights didn't work.Nothing.She used her cellphone to call for help and was waiting patiently in the car "when a man pulls along side of me and screamed, 'Miss, get out of your car! Your car is on fire!' I jumped out moments before it exploded," said Jackson, 24.It all happened so quickly.During the excitement her rescuer...