PDF.js viewer triggers localStorage access error in Chrome's private browsing mode

When testing an LMS PDF assignment in Incognito Mode in Chrome I noticed an error from Via3's copy of PDF.js in the console:

In this environment, any attempt to access `window.localStorage` generates the following error:

```
Uncaught DOMException: Failed to read the 'localStorage' property from 'Window': Access is denied for this document.
```

Chrome version: 90.0.4430.19 (Official Build) dev (x86_64)

The PDF content still loaded though and I haven't noticed any adverse effects on using Hypothesis yet.