Hi all, before I start let me thank you for all the time devoted to this software!

On my website I have an issue since Joomla 3.7.5. This problem persists in Joomla 3.8.0. Looking back in my logfiles, the problem did not occur with 3.7.4 and earlier.

Steps to reproduce the issue

Create a menu item of type "Category Blog", filtered by one Tag, 0 "Leading Articles" and 5 "Intro Articles". When the number of articles tagged by this Tag is less than 5, the page will not show.

Expected result

A page with tagged articles in blog layout.

Actual result

Http error 500. Setting $error_reporting = 'development' does not produce additional php error text.

System information (as much as possible)

Joomla 3.7.5 and 3.8.0, template Purity III v 1.2.0, T3 framework v 2.6.7, Jotcache 5.3.2, and a good number of other packages which can't imagine being involved in this problem. Host is Centos 7.4, Apache 2.4.8, PHP 7.1.9 and mariadb 5.5.56.