Fix console errors
@stanzabird this fixes the errors you talked about
I'm getting this on the stdout of LW which uses the new about box:
Missing chrome or resource URL: chrome://branding/content/about-logo.png Missing chrome or resource URL: chrome://branding/content/firefox-wordmark.svg Missing chrome or resource URL: chrome://branding/content/aboutDialog.css JavaScript error: chrome://browser/content/aboutDialog.js, line 89: TypeError: relNotesLink is null