Error When Registering for Events "Expected one Contribution but found 25"

After upgrading from CiviCRM 4.6.24 to CiviCRM 4.7.18 on Drupal (7.52) we are getting the error "Expected one Contribution but found 25" whenever registering for an event with an event page.

I think that a related issue is that no new transactions are showing up as completed even if the  contribution_status_id is equal to one which corresponds to the completed status.  I have checked the database and nothing appears to be incorrect from that perspective.  

I did not get any errors when upgrading CiviCRM as described above.  

I have tested while logged in, not logged in, with and without price sets.

I am running Apache 2.4.25 with PHP 5.6.30.

Attached is the complete error that I have from Watchdog.  

Thanks,

Josh