Appears to be introduced by the fix for bug 16622703 at this location specifically: https://searchfox.org/comm-central/diff/6fca3093634e3bb2ccb3e946be59c4033f9cf332/mail/components/preferences/privacy.js#140
Bug 1659335 Comment 6 Edit History
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Appears to be introduced by the fix for bug 1622703 at this location specifically: https://searchfox.org/comm-central/diff/6fca3093634e3bb2ccb3e946be59c4033f9cf332/mail/components/preferences/privacy.js#140