InvalidParameterException after deleting users from users_entity table

I recently added a large number of users using the upload_users plugin. However, I realized that I had mistakenly uploaded a csv containing md5 hashes of the users' passwords rather than the plaintext. I tried to delete these users by dropping their corresponding rows in the users_entity table but now I get the error "InvalidParameterException: All files must have an owner!" when I visit the users administration page. What is the best thing for me to do at this point?