Fix possible PHP error notice

Author: iMattPro

event/listener.php

@@ -125,7 +125,7 @@ public function add_googleanalytics_configs($event)
 	*/
 	public function validate_googleanalytics_id($event)
 	{
-		$input = $event['cfg_array']['googleanalytics_id'];
+		$input = isset($event['cfg_array']['googleanalytics_id']) ? $event['cfg_array']['googleanalytics_id'] : '';
 
 		// Check if the validate test is for google_analytics
 		if ($input !== '' && $event['config_definition']['validate'] === 'googleanalytics_id')

tests/event/listener_test.php

@@ -12,7 +12,7 @@
 
 require_once __DIR__ . '/../../../../../includes/functions_acp.php';
 
-class event_listener_test extends \phpbb_test_case
+class listener_test extends \phpbb_test_case
 {
 	/** @var \phpbb\googleanalytics\event\listener */
 	protected $listener;
@@ -199,6 +199,11 @@ public function validate_googleanalytics_id_data()
 				array('googleanalytics_id' => 'foo-bar-foo'),
 				array('ACP_GOOGLEANALYTICS_ID_INVALID'),
 			),
+			array(
+				// no googleanalytics_id, no error
+				array('foo' => 'bar'),
+				array(),
+			),
 		);
 	}
 
@@ -211,7 +216,7 @@ public function test_validate_googleanalytics_id($cfg_array, $expected_error)
 	{
 		$this->set_listener();
 
-		$config_name = 'googleanalytics_id';
+		$config_name = key($cfg_array);
 		$config_definition = array('validate' => 'googleanalytics_id');
 		$error = array();