Check obj exists before attempting to perform "querySelectorAll"

fixes: Uncaught TypeError: Cannot read property 'querySelectorAll' of undefined
when mail widget is used on dashboard and a user isn't logged in
Better fix
userHighlight.options.dontHighlightFirstComment

Don't highlight the "first commenter" user in their first comment by default.
fix /r/RESIssues+Enhancement/submit wizard

didn't get updated with RESUtils.createElementWithID
Removed tests.js references in manifests for Chrome, Opera, and FF.
Fix issue with Reddit's updated stylesheet
Merge pull request #816 from andytuba/dontHighlightFirstCommenter

userHighlight.options.dontHighlightFirstComment
Merge pull request #833 from SirCmpwn/fix-style

(Critical) Fix issue with Reddit's updated stylesheet and inline images
changed body to #header for overflow-x: hidden to fix issue with scrolling screen
Merge pull request #831 from brettp/no_tests

Removed tests.js references in manifests for Chrome, Opera, and FF.
Clean up utils.js to avoid variable issues
Update Flickr expando regex; fixes #825
Disable NER on wiki pages; fixes #848
Merge pull request #858 from mc10/never-ending-reddit

Disable NER on wiki pages
Delete unused Firefox README files
Copyedit and update documentation
Use ndashes for file lists
Rework title and introduction
Copyedit and fix typos
Avoid using a "here" link