bugfix: When obtaining a UserID for the state array prior to running authproc...

bugfix: When obtaining a UserID for the state array prior to running authproc filters, if the source attribute had multiple values a warning was logged but the UserID was still recorded.

lib/SimpleSAML/Auth/ProcessingChain.php

@@ -344,6 +344,7 @@ class SimpleSAML_Auth_ProcessingChain {
 
 		if (count($uid) > 1) {
 			SimpleSAML\Logger::warning('Multiple attribute values for user id attribute [' . $attributeName . '].');
+			return;
 		}
 
 		$uid = $uid[0];