Issue title: Null in settings panel
 Issue body: The problem with the latest version might have introduced a new "setting" in the setting menu. @eproxus, @message, could you please confirm if you see a "Null" setting in the menu after the last update?

 Comments: 
 Comment 0: In case you do, could you please take the following steps?
1. Right-click on any page element and select _Inspect Element_.
2. In the panel that opens up, select the _Resources_ tab.
3. Click on the small arrow next to _Local Storage_ on the left side of the panel.
4. Click on `http://news.ycombinator.com`
5. Please double-click each of the two strings of code next to the `hnspecial-defaults` and `hnspecial-settings` rows in the right side of the panel and copy and paste the code here.

I'd like to see this code so I can debug this issue and possibly provide a fix if needed. Many thanks in advance.

 Comment 1: Never mind, I think I fixed this. New version should be out soon, please let me know if you continue seeing the setting afterwards.

 Comment 2: Temporarily saw it, but it is now gone again with the latest version. Thanks for the quick fixes! :smile: 

 Comment 3: No problem! Glad to see it's gone!

{'source': 'GithubIssues', 'repo_name_with_owner': 'gabrielecirulli/hn-special', 'issue_id': 28148368, 'repo_stars': 324.0}