List of Campaigns blank after upgrading to 3.5.1

Version 3.5.1
Tried with Chrome, Edge, Firefox
Upgrade appeared to be successful but now have a blank page when I access the “List of Campaigns” link. The source code for the resulting page does have lots of content but none of the browers I’ve tried displays anything.

All of the rest of the pages seem to work.

Further information: The database table phplist_message contains all of my campaigns. It also has a blank campaign at the last position. That campaign is not present in the database prior to the upgrade. (I have a backup copy of the database.)

Furthermore, the titles of the campaigns do not appear in the html text that is present in the “List of Campaigns” page.

Downgrading from PHP 7.1 to PHP 7.0 fixed this.