If an empty file ends up in your collection, Anki won’t detect it. For example:
cd ~/.local/share/Anki2/<username>/collection.media
touch xxxxxxx.jpg
# run media check
# result: nothing detected.
Why does Anki behave this way? I think it would be more convenient if empty files were removed. I have several empty files, probably caused by ffmpeg errors when I used mpvacious to create Anki cards from movies.
I wouldn’t delete it either. You never know why the data wasn’t read, or why there were blocks, and so on. And if you delete it, you’ll only get complaints.
If you delete an empty file that is referenced in a note, you’ll next get an error message about the missing file. I recommend that an empty file not referenced be reported as unused, but not removed. If it is referenced, but it’s empty, that should also be pointed out.