Merge pull request #153 from cmaglie/fix_windows_enumerator

windows: Avoid panic if USB Product name is empty

enumerator/usb_windows.go

@@ -347,11 +347,13 @@ func retrievePortDetailsFromDevInfo(device *deviceInfo, details *PortDetails) er
 		the result of spdrpFriendlyName is therefore unique and suitable as an alternative string to for a port choice */
 	n := uint32(0)
 	setupDiGetDeviceRegistryProperty(device.set, &device.data, spdrpFriendlyName /* spdrpDeviceDesc */, nil, nil, 0, &n)
+	if n > 0 {
 		buff := make([]uint16, n*2)
 		buffP := (*byte)(unsafe.Pointer(&buff[0]))
 		if setupDiGetDeviceRegistryProperty(device.set, &device.data, spdrpFriendlyName /* spdrpDeviceDesc */, nil, buffP, n, &n) {
 			details.Product = syscall.UTF16ToString(buff[:])
 		}
+	}
 
 	return nil
 }