Problem: theme generation fails

[sappo]

The following error occurs if I try to use this theme:

warn: Filter "fileExists" is deprecated, use "fileExists(filename)"  
error: error while generating page "README.md": 

Template render error: (/tmp/book/_layouts/website/page.html)
  TypeError: Path must be a string. Received undefined

More details https://www.gitbook.com/book/sappo/rfc/build/574be31ce3ca0e1000bd6713

[xiasenhai]

And the README.md

[Soreine]

@sappo I think I have found the source of your bug, and moved it to this issue #18