Add variable undeclared ($url) (#3164)

* Add variable undeclared ($url)

* Update ZipException.php

* modify

app/Exceptions/ZipException.php

@@ -4,7 +4,7 @@ class FreshRSS_Zip_Exception extends Exception {
 	private $zipErrorCode = 0;
 
 	public function __construct($zipErrorCode) {
-		parent::__construct('ZIP error! ' . $url, 2141);
+		parent::__construct('ZIP error!', 2141);
 		$this->zipErrorCode = $zipErrorCode;
 	}