When I run update this is the PDO I've received every time from a pending update for mailsystem-7.x-2.34.tar.gz upgrading to mailsystem-7.x-3.0-alpha1.tar.gz:

The following updates returned messages

mailsystem module

Update #7300
Failed: PDOException: SQLSTATE[42000]: Syntax error or access violation: 1064 You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '))' at line 1: DELETE FROM {registry} WHERE (name IN ()) ; Array ( ) in mailsystem_update_7300() (line 100 of /home/mysite/public_html/sites/all/modules/mailsystem/mailsystem.install).

Files: 
CommentFileSizeAuthor
#2 1905736-mailsystem-7300.patch456 bytesfearlsgroove

Comments

I got the same error.

Version:7.x-2.34» 7.x-3.0-alpha1
Component:Module compatibility» Code
Issue summary:View changes
Status:Active» Needs review
StatusFileSize
new456 bytes

If there are no generated classes to delete, it shouldn't try to delete those.