Steps to reproduce:
Create Item or item prototype with parameters:

			[
				'hostid' => self::HOSTID,
				'ruleid' => self::RULEID,
				'name' => '5_Aggregate',
				'key_' => 'grpavg["host group", [{#KEY}], avg, last]',
				'type' => 8,
				'value_type' => 0,
				'delay' => '9m'
			],

Result:
Item was created successfully and is present in Frontend with item type - Unknown.

Expected:
Error message should be generated while create or update attempt and item should not be created.