Cannot read property 'length' of undefined

[ehmicky]

Some builds are showing the following error:

Cannot read property 'length' of undefined 
    /opt/buildhome/.netlify-build-plugins/node_modules/urltools/lib/index.js:8:35 Object.exports.getCommonPrefix
    /opt/buildhome/.netlify-build-plugins/node_modules/urltools/lib/index.js:42:32 exports.buildRootRelativeUrl
    /opt/buildhome/.netlify-build-plugins/node_modules/hyperlink/lib/getModifiedHref.js:24:14 getModifiedHref
    /opt/buildhome/.netlify-build-plugins/node_modules/hyperlink/lib/index.js:747:17 hyperlink
    internal/process/task_queues.js:62:5 runNextTicks
    internal/timers.js:429:9 processImmediate
    /opt/buildhome/.netlify-build-plugins/node_modules/netlify-plugin-checklinks/lib/index.js:46:5 async onPostBuild
    src/plugins/child/run.js:17:3 async Object.run
    src/plugins/child/main.js:38:38 async handleEvent
    src/plugins/ipc.js:97:9 async process.<anonymous>

The build logs do not show additional information, except that the checkExternal option was set to true.

Looks like this might be bug inside hyperlink? Do you know what the error might be?

[flossypurse]

This error is super frustrating.
We get this from time to time and never really know what is causing it.
Any way to start by adding some debug logs to figure out why this happens?