tests: Avoid using dynamic properties

Signed-off-by: Julius Härtl <jus@bitgrid.net>

tests/unit/Middleware/ExceptionMiddlewareTest.php

@@ -41,6 +41,7 @@ class ExceptionMiddlewareTest extends \Test\TestCase {
 	private $logger;
 	/** @var IConfig */
 	private $config;
+	private $request;
 	private $controller;
 	private $exceptionMiddleware;