I think this is an old bug because I can reproduce this on Nightly 2016-01-01. [My patch](https://hg.mozilla.org/mozilla-central/rev/f3eb9d545987) in Bug 1550869 (landed in 2019-06-18) might hide it, and Bug 1745435 uncover it again.
Bug 1754459 Comment 10 Edit History
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I think this is an old bug because I can reproduce this on Nightly 2016-01-01. [My patch](https://hg.mozilla.org/mozilla-central/rev/f3eb9d545987) in Bug 1550869 (landed in 2019-06-18) might hide it, and Bug 1745435 reveals it again.