Since I wasn't looking forward to finding my latest backup and restoring my old version, and since I knew I would still have the problem even after I restored my old WordPress version, I set out to find the problem with my excellent debugging skills. 😉
I always start with plugins since they are often the culprit and they are easier to debug than themes. I started deleting plugins that I didn't really want or need hoping that they would be the culprit and I could just get rid of them and get my site back to good. Nope. That didn't work. Still had the problem after deleting all the plugins I didn't really want.
Then I moved the plugin that I had created outside the plugin folder to see if that fixed the problem. Bam! My site was back up and running. But, I really want MY plugin to work and now I'm really curious what I've done wrong.
I move my plugin back into the plugin folder and look through the code to see if I can figure out what might be causing the problem. Since I know the error is occurring on this line in the wp-includes/query.php file:
// $wp_query->reset_postdata(); //
I reason that my problem might be with one of the $wp_query calls I'm using in my code. My eyes immediately went to the
wp_reset_query() line I had in my file. I commented out this line and Boom! my site is back up and running. Does my code need this line? I hope not because apparently this line doesn't work in 3.7 OR I had the line in the wrong place in my code initially. I probably didn't need it. It's a plugin I created a while ago and I probably copied some of that code from another site. I'm sure I didn't really understand what that line was doing.
I'll give my site a thorough testing to make sure I don't need that line of code. If I find that I do need it, it will make for another post. Until then, my site is working and I'm happy.