Steps to reproduce DB:

createuser --pwprompt zabbix
createdb zabbix_test
psql -c "ALTER DATABASE zabbix_test OWNER TO zabbix;"
psql zabbix_test -c 'CREATE EXTENSION timescaledb VERSION "2.15.3";'
psql zabbix_test -c "SELECT public.timescaledb_pre_restore();" -f /tmp/zabbix_dump_reproducible.sql -c "SELECT public.timescaledb_post_restore();"

DB dump available in comment.

Two users available:

superadmin user - Admin Secret1234!
admin user - tester123 Tere123456!

Steps to reproduce bug:

• Login as tester123
• Find template Module ICMP Ping template and try clone it. When you will press "Add" button you will met an error:
  
  the text of the error: Reproduced error_text.txt
• Try to Export the template, you should meet 500 error.
• Try clone some of others two templates you will succeed.
• Try export some of others of two templates you will succeed.
• Create any host and link some of free template to the host
• Try to clone the template. When it was unlinked you could do it, now you couldn't.
• Try export the template - the 500 error
• Unlink and delete the template from the host.
• Now you can clone it and export too
• Login as Admin
• Find and clone Module ICMP Ping template. You should success
• Now login as tester123 again
• Try clone linked template Module ICMP Ping, now it should be cloned without errors.

Expected:
Expected that admin user could clone linked templates without errors.