Problem description: When opening section "Configure DB connection" of the setup.php view field "Database schema" is missing in case if PostgreSQL is the only available option in field "Database type". The problem is present only for 4.0 release 

Steps to reproduce:

1. Have a Zabbix installation with only PostgreSQL configured on the machine
2. Navigate to setup.php view
3. Open section "Configure DB connection"
4. Make sure that "PostgreSQL" is the only available option in field "Database type"
5. Try to locate field "Database schema"

Result: "Database schema" field is missing
Expected:
"Database schema" field should be present because "Database type" is set to "PostgreSQL"

Example: