Any notices in that file happen before `WP_DEBUG` takes effect, and should not be displayed with the `error_reporting` level previously set in `wp-load.php`.
Adding the class when there is no notice displayed results in extra padding under the admin bar, which should be avoided.
Follow-up to [20102], [21025], [26620], [47745].
Props akissz, tw2113, laxman-prajapati, sabernhardt, johnbillion, SergeyBiryukov.
Fixes#51073.
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