Don't fail if localStorage cannot be used.

[lddubeau]

Previously, if localStorage was not accessible for whatever reason, then the initialization of the extension would fail. This would leave the extension with a #request-list that had no width set and no ability to resize it. This was okay so long as the URLs in the request list were relatively short but for very long URLs the request list would take more than the width of the frame that DevTools made available for it and would thus be unusable.