Steps to reproduce:

1. Put certificate (PEM) file into default path (/usr/share/zabbix/ssl/certs)
2. Create HTTP agent item
3. Fill in the SSL certificate file field

Result:

Works fine when using Test button:

But item is not supported anyway:

**

Log after increasing log level:

_{886679:20240621:115046.124 using SSL certificate file: '(null)/cert.pem'}

It was tested with default and custom values of SSLCertLocation parameter, every time the same error.

Expected:
It should work in both cases.

It was tested on Rocky Linux 9 and Ubuntu 22.04. In Zabbix 6.4 everything works fine.