[An extra null pointer check is not needed](https://stackoverflow.com/questions/18775608/free-a-null-pointer-anyway-or-check-first "Free a null pointer anyway or check first?") in [the function “stopQat”](https://github.com/intel/QATzip/blob/7c3a08ac1e7715198ea4d435d30426226cf98774/src/qatzip.c#L450-L453 "Update candidate").
