Make validateIdentifiers a truthy experience in both Agent and Group

Author: ht2

src/Agent.php

@@ -34,7 +34,7 @@ protected function identifierError($used_identifiers) {
   }
 
   protected function validateIdentifiers($used_identifiers) {
-    return $used_identifiers !== 1;
+    return $used_identifiers === 1;
   }
 
   public function validate() {
@@ -44,7 +44,7 @@ public function validate() {
     $used_identifiers = $this->countIdentifiers();
 
     // Checks that only one identifier is used.
-    if ($this->validateIdentifiers($used_identifiers)) {
+    if (!$this->validateIdentifiers($used_identifiers)) {
       $errors[] = new Error($this->identifierError($used_identifiers));
     }
 

src/Group.php

@@ -15,7 +15,7 @@ protected function identifierError($used_identifiers) {
   protected function validateIdentifiers($used_identifiers) {
     $members = $this->getPropValue('member') ?: null;
     $validateIdentifiers = parent::validateIdentifiers($used_identifiers);
-    $validateMembers = $members === null || count($members) === 0;
+    $validateMembers = $members !== null && count($members) > 0;
     return $validateIdentifiers && $validateMembers;
   }
 }