Throwing notices from SQL problem

Using latest version of WP and Draft Notify I’m getting notices thrown when saving posts:

Notice: Trying to get property of non-object in … wp-content\plugins\draft-notify\draft-notify.php on line 58

Looking at the query in the code I think there’s a problem with how you’ve written your joins – you’ve got three LEFT JOINS to usermeta but you’re selecting from the posts and users table without joining them. If I fix this, the query works.

I may have misunderstood what you’re doing with this query but there’s clearly a problem where no rows are being returned which is breaking the next line of code.