type mistmatch in system_logger.nim
```
C:\Users\Altarrel\.nimble\pkgs\nimx-0.1\nimx\system_logger.nim(35, 76) Error: type mismatch: got <nil> but expected 'string'
```

I get this error using the example in the README.

OS: Windows 10 64 bit
Output of `nim -v`:
```
Nim Compiler Version 0.18.1 [Windows: amd64]
Compiled at 2018-08-19
Copyright (c) 2006-2018 by Andreas Rumpf

git hash: b5171f57ef00bffb12387d7daf3487c5e07645f9
active boot switches: -d:release
```