Steps to reproduce the issue

1. create an article with the title "Hello finder", without introtext but with fulltext that contains several random sentences and the word "foobar"
2. call php cli/finder_indexer.php
3. search for "foobar"

Expected result

In the results page I want to see the title "Hello finder", followed by the description of the article, with the word "foobar" highlighted

Actual result

In the results page we see the title "Hello finder", but no description of the result

System information (as much as possible)

Database Type: mysql
Database Version: 5.6.45
Database Collation: utf8_general_ci
Database Connection Collation utf8mb4_general_ci
PHP Version 7.4.3
Web Server Apache/2.4.41 (FreeBSD) OpenSSL/1.0.2s mod_fcgid/2.3.9
WebServer to PHP Interface cgi-fcgi
Joomla! Version Joomla! 3.9.23 Stable [ Amani ] 24-November-2020 15:00 GMT
Joomla! Platform Version Joomla Platform 13.1.0 Stable [ Curiosity ] 24-Apr-2013 00:00 GMT
User Agent Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:84.0) Gecko/20100101 Firefox/84.0

Additional comments

I found the source of this issue in components/com_finder/tmpl/search/default_result.php:33: the && operation only turns true if both parts are true. It should be replaced by the || operation.

In theory I would expect every article to have introtext and fulltext. In reality this is not a save assumption. On the site where I found this someone committed articles without introtext.