Empty Password Entries

We recently had a site that required a user table import of ~15K users. Unfortunately, a good portion of the password fields were empty when importing. We initially thought about doing a little cleanup of the csv and just dump in a generic password to all the empty passwords and reimport, but our problem there lies with all the changes that have happened to the database since it was imported. In the database it shows that there is in fact a password that was generated for these empty cells, so is there a generic password that the plugin uses if the cell is empty? Basically the users that had empty passwords can’t use any of the password reseting features, and its having to be done from the backend by the site’s admin, which is not ideal as theres probably 1000’s of people who may face this. Any help would be greatly appreciated!