TypeError: Cannot read properties of undefined (reading 'split')

[dotherightthing]

When I load https://sites.google.com/view/search-gas-libraries I see the following error in the Developer console:

TypeError: Cannot read properties of undefined (reading 'split')
    at inner-frame-minified.html?jsh=m%3B%2F_%2Fscs%2Fapps-static%2F_%2Fjs%2Fk%3Doz.gapi.en_GB.YRwQQlVPV8A.O%2Fam%3DAQ%2Fd%3D1%2Frs%3DAGLTcCMir3wdUyDFk2lap4KYegtAhqGb7A%2Fm%3D__features__:63:30
    at Array.reduce (<anonymous>)
    at fromANDREWROBERTSList (inner-frame-minified.html?jsh=m%3B%2F_%2Fscs%2Fapps-static%2F_%2Fjs%2Fk%3Doz.gapi.en_GB.YRwQQlVPV8A.O%2Fam%3DAQ%2Fd%3D1%2Frs%3DAGLTcCMir3wdUyDFk2lap4KYegtAhqGb7A%2Fm%3D__features__:48:24)
    at inner-frame-minified.html?jsh=m%3B%2F_%2Fscs%2Fapps-static%2F_%2Fjs%2Fk%3Doz.gapi.en_GB.YRwQQlVPV8A.O%2Fam%3DAQ%2Fd%3D1%2Frs%3DAGLTcCMir3wdUyDFk2lap4KYegtAhqGb7A%2Fm%3D__features__:20:47