Undefined array key "comment_content"

[edent]

If a WebMention doesn't have any content (for example a like or repost) then WordPress complains with

PHP Warning: Undefined array key "comment_content" in /home/blog/wp-includes/comment.php on line 2130

Would it make sense to either add a blank space or the text "so-and-so liked this on example.com"?

[pfefferle]

This is weird, because it should at least have the key... it should be empty, but not inexistent.