processImports set to false and using @import results in TypeError: Cannot read property 'rules' of undefined

I've looked through the issues, but couldn't find something similar. The below code used to work in less 2.x.

const less = require('less');
const raw = ` @import url('https://fonts.googleapis.com/css?family=Open+Sans:400,700');`;

less.render(raw, { processImports: false })
    .then(() => console.info('Less ok!'))
    .catch(error => console.error('Less failed!', error));

When trying this with less 3.11.1 it fails with TypeError: Cannot read property 'rules' of undefined on the following less-code from less.cjs.js:

else {
  ruleset = new Ruleset(null, copyArray(this.root.rules));
  ruleset.evalImports(context);
  return this.features ? new Media(ruleset.rules, this.features.value) : ruleset.rules;
} 

this.root seems to be undefined. I'm just wondering if it's something I did wrong on my end or that it's a bug we can fix?

Setting processImports to true > Ok
Adding more css/less > Same error.

Managed to fix it by changing the less code to

else if (this.root) {
  ruleset = new Ruleset(null, copyArray(this.root.rules));
  ruleset.evalImports(context);
  return this.features ? new Media(ruleset.rules, this.features.value) : ruleset.rules;
} else { return []; }

But I'm not sure if that's the best approach here, there might be an underlying bug somewhere.

Reproduce the issue with the provided less.render example using processImports: false, then inspect less.cjs.js around the ruleset and evalImports branch where this.root is accessed. Done means the external @import no longer throws a TypeError when imports are disabled, while the existing processImports: true behavior remains working.