when setNonExistentCodeSystemSeverity=ERROR and an unknown CodeSystem is used on a FHIR resource, the validation doesn't return an ERROR as expected, it completes with no issues.

To Reproduce

1. setNonExistentCodeSystemSeverity=ERROR in UnknownCodeSystemWarningValidationSupport
2. Try to validate the following Medication resource, which contains an unknown codesystem, using the Medication/$validate operation.

{
    "resourceType": "Medication",
	"text": {
	    "status": "generated",
	    "div": "<div xmlns=\"http://www.w3.org/1999/xhtml\">empty</div>"
	},
        "code": {
        "coding":  [
            {
		"system": "http://test123.org",
		"code": "00559407",
		"display": "TYLENOL EXTRA STRENGTH"
            }
        ]
    }
}

Actual: The validation completes without any issues.

Expected: An error should be generated.

Note: when setNonExistentCodeSystemSeverity=WARNING, a warning for the unknown code system is generated as expected.