Greetings,
I was just about to suggest that!
There are, unfortunately, many other places in the ListMail code where the auto_increment is expected to work with '' instead of NULL.
A global search of all files for "insert into" should find all of the statements to modify. Basically the first values field should be changed from '' (two apostrophes) to NULL
If you need help applying this fix you can submit your info
here.
I have made a note for future updates.
Regards