fix bug that was almost impossible to hit in prtDataSetInMem.m
fix bug that was almost impossible to hit in prtDataSetInMem.m

covartech/PRT,jpalves/PRT,covartech/PRT,jpalves/PRT,covartech/PRT,covartech/PRT,jpalves/PRT,covartech/PRT,covartech/PRT,jpalves/PRT,jpalves/PRT,jpalves/PRT