CRASH: TypeError: Cannot set property 'contents' of undefined

[sbrl]

If I try to setup docpress, I keep getting this crash:

/path/to/project/node_modules/docpress/bin/docpress:16
      if (err) throw err
               ^

TypeError: Cannot set property 'contents' of undefined
    at eachCons (/path/to/project/node_modules/docpress-base/index.js:219:19)
    at keys.forEach (/path/to/project/node_modules/docpress-base/lib/helpers/each_cons.js:11:5)
    at Array.forEach (<anonymous>)
    at eachCons (/path/to/project/node_modules/docpress-base/lib/helpers/each_cons.js:8:8)
    at Object.relayout (/path/to/project/node_modules/docpress-base/index.js:197:3)
    at Ware.<anonymous> (/path/to/project/node_modules/wrap-fn/index.js:45:19)
    at next (/path/to/project/node_modules/ware/lib/index.js:85:20)
    at /path/to/project/node_modules/wrap-fn/index.js:121:18
    at callback (/path/to/project/node_modules/docpress-base/index.js:104:5)
    at useCache (/path/to/project/node_modules/docpress-base/lib/helpers/use_cache.js:6:5)

Project in question: https://github.com/ConnectedHumber/Air-Quality-Web/tree/new-docs (don't forget to checkout the new-docs branch).

Commands used:

npm install
node_modules/docpress/bin/docpress build