[TIDOC-1866] Fixed issue with missing platform filter settings data

## Verification steps

1. In the JSDuck directory, create a new branch from a pre-platform filter commit, e.g.:
    
        git checkout -b pre-filter aeaf1cc364e7b16256f200e8f6a9bb7de867f517

2. Build docs locally and open in Chrome, e.g.

        $ cd doctools
        $ sh deploy.sh
        $ open dist/titanium/3.0/index.html

3. Open an API reference page.
3. Clear LocalStorage data by opening the JavaScript Inspector (Cmd+Option+J) and entering the following command:

        localStorage.clear();

4. Reload the doc pages in Chrome to reset the localstorage data to it's default state, as a "normal" user would have installed before the platform filter update. Check that you see all expected methods/properties for the current API reference page.
5. To reproduce the original issue, checkout the JSDuck master branch containing the breaking changes and build docs again.
6. Reload the API page in Chrome. The API methods/properties should have disappeared, and all the platform filter checkboxes should be "off"/"unchecked". (Note: Don't make changes to the platform filters at this point, as it will corrupt the verification steps). This is because the filtering logic is out of sync with the local storage data.
5. To see the fix applied, checkout the TIDOC-1866 pull request branch and build docs again:
7. Reload the same API page you have open in Chrome. 

Verify that all platform filter checkboxes are on/checked, and the missing methods/properties are visible again.