`nimble doc` failed with UnpackError
I have run into this problem with several projects, even empty projects just created:
```
nimble init # press enter to use the default values
nimble doc
```
I got:
```
options.nim(185)         get
Error: unhandled exception: Can't obtain a value from a `none` [UnpackError]
```

see also: https://github.com/nim-lang/Nim/issues/14281
