fixed C++ compiler error reported by clang 5.1
fixed C++ compiler error reported by clang 5.1

wdv4758h/ZipPy,wdv4758h/ZipPy,wdv4758h/ZipPy,wdv4758h/ZipPy,wdv4758h/ZipPy,wdv4758h/ZipPy,wdv4758h/ZipPy,wdv4758h/ZipPy