Check for empty Groups Key

Right now if you don't set a Groups Key in the integration configuration then $this->getKey() will log "PHP Notice:  Undefined index:  " because it's being asked to look for a blank key. This commit first checks whether the key is set before passing it to getKey() to prevent this Notice.

Author: RussellAult

User/GenericOAuth2UserProvider.php

@@ -157,7 +157,13 @@ public function getEmail()
      */
     public function getExternalGroupIds()
     {
-        $groups = $this->getKey('oauth2_key_groups');
+        $key = 'oauth2_key_groups';
+        
+        if (empty($this->configModel->get($key))) {
+            return array();
+        }
+        
+        $groups = $this->getKey($key);
 
         if (empty($groups)) {
             $this->logger->debug('OAuth2: '.$this->getUsername().' has no groups');