fix error caused by `bytesWritten` is null
fix error caused by `bytesWritten` is null

fix error  caused by `bytesWritten` is null

johanneslumpe/react-native-fs,itinance/react-native-fs,johanneslumpe/react-native-fs,johanneslumpe/react-native-fs,veeloinc/react-native-fs,itinance/react-native-fs,itinance/react-native-fs,veeloinc/react-native-fs,itinance/react-native-fs,veeloinc/react-native-fs