R1:2e8a5e843f95

Recover when cookies are disabled in Firefox and accessing localStorage throws

Summary:
Ref T13216. See PHI985. If you disable cookies in Firefox, accessing `window.localStorage` throws an exception. Currently, this pretty much kills all scripts on the page.

Instead, catch and ignore this, as though `window.localStorage` was not defined.

Test Plan:
- Set Firefox to "no cookies".
- Loaded any page while logged out.
- Before: JS fatal early in the stack.
- After: page loads and JS works.