removed unused property from Session

cleanup after #1479

framework/yii/web/Session.php

@@ -112,19 +112,15 @@ class Session extends Component implements \IteratorAggregate, \ArrayAccess, \Co
 		return false;
 	}
 
-	private $_opened = false;
-
 	/**
 	 * Starts the session.
 	 */
 	public function open()
 	{
 		if (session_status() == PHP_SESSION_ACTIVE) {
-			$this->_opened = true;
 			return;
 		}
 
-		if (!$this->_opened) {
 		if ($this->getUseCustomStorage()) {
 			@session_set_save_handler(
 				[$this, 'openSession'],
@@ -141,23 +137,19 @@ class Session extends Component implements \IteratorAggregate, \ArrayAccess, \Co
 		@session_start();
 
 		if (session_id() == '') {
-				$this->_opened = false;
 			$error = error_get_last();
 			$message = isset($error['message']) ? $error['message'] : 'Failed to start session.';
 			Yii::error($message, __METHOD__);
 		} else {
-				$this->_opened = true;
 			$this->updateFlashCounters();
 		}
 	}
-	}
 
 	/**
 	 * Ends the current session and store session data.
 	 */
 	public function close()
 	{
-		$this->_opened = false;
 		if (session_id() !== '') {
 			@session_write_close();
 		}