Disabling `MOZ_DATA_REPORTING` results in the `PREF_UPLOAD_ENABLED` pref not
being loaded with `Preferences.add`. This means
`Preferences.get(PREF_UPLOAD_ENABLED)` can possibly be `null`, which was
previously not handled and resulted in an error for the whole privacy.js file.
So only call `dataCollectionCheckboxHandler` for the `privateAttribution`
checkbox if `MOZ_DATA_REPORTING` is enabled (otherwise the `privateAttribution`
checkbox also just doesn't exist). Also move the call into separate
`initPrivateAttributionCheckbox` function to be more consistent with previous
code.
Differential Revision: https://phabricator.services.mozilla.com/D218265
3809a1239b
