[push-api] Resolve with null if not registered. (#101)

Issue #96 
You can merge this Pull Request by running:

  git pull https://github.com/mvano/push-api NullableRegistration

Or you can view, comment on it, or merge it online at:

  https://github.com/w3c/push-api/pull/101

-- Commit Summary --

  * Resolve with null if not registered.

-- File Changes --

    M index.html (10)

-- Patch Links --

https://github.com/w3c/push-api/pull/101.patch
https://github.com/w3c/push-api/pull/101.diff

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Reply to this email directly or view it on GitHub:
https://github.com/w3c/push-api/pull/101