Why did the project stop running on node?

Question

Node.js

There is a project on node 8. Run by yarn.
At some point it stopped working with the following error:

Starting dev server...
(node:6687) UnhandledPromiseRejectionWarning: TypeError: Cannot read property 'map' of undefined
    at getVariantCss ((cut)/node_modules/google-fonts-webpack-plugin/src/GoogleWebfonts.js:23:25)
    at variants.forEach.variant ((cut)/node_modules/google-fonts-webpack-plugin/src/GoogleWebfonts.js:70:16)
    at Array.forEach (<anonymous>)
    at font.info.then.info ((cut)/node_modules/google-fonts-webpack-plugin/src/GoogleWebfonts.js:67:14)
    at <anonymous>
    at process._tickCallback (internal/process/next_tick.js:189:7)

Surprisingly, all copies of the project, including the old ones on different machines (debian/ubutnu/macos), also stopped running. Googling this error doesn't turn up anything.