There are some empty posts from the Community user in its activity history:
What are those? If it's something deleted should it be marked appropriately instead of leaving the rows blank?
I can answer what those are: they're orphan wikis. So this is perhaps another variation of Orphaned tag wiki edits have broken activity entries.
It turns out you can find the post IDs via the browser tools:
and navigating to e.g. https://meta.stackexchange.com/posts/359539/revisions will confirm:
The posts are not deleted (and even continue to give +2 reputation for suggested edits, IIRC). The problem seems not limited to Community, see e.g. this page on my profile – but you noticed that a couple of years ago already.