Fix unhandled promise rejection when calling read on Windows.
Fix unhandled promise rejection when calling read on Windows.

Without this change, following error is signaled:
(node:12996) UnhandledPromiseRejectionWarning: Unhandled promise rejection (rejection id: 2): TypeError: First argument must be an int

node-serialport/node-serialport,node-serialport/node-serialport,voodootikigod/node-serialport,EmergingTechnologyAdvisors/node-serialport,EmergingTechnologyAdvisors/node-serialport,EmergingTechnologyAdvisors/node-serialport,node-serialport/node-serialport,node-serialport/node-serialport,EmergingTechnologyAdvisors/node-serialport,node-serialport/node-serialport,voodootikigod/node-serialport,voodootikigod/node-serialport,EmergingTechnologyAdvisors/node-serialport,voodootikigod/node-serialport