Fix feature detection for IE

alsciende · stof · commit b35658b1ff90 · 2016-06-13T13:03:01.000+02:00
operator `!` has higher precedence (4) than operator `in` (8). Parentheses are mandatory here.
diff --git a/src/Symfony/Bundle/WebProfilerBundle/Resources/views/Profiler/base_js.html.twig b/src/Symfony/Bundle/WebProfilerBundle/Resources/views/Profiler/base_js.html.twig
@@ -209,7 +209,7 @@
         var addEventListener;
 
         var el = document.createElement('div');
-        if (!'addEventListener' in el) {
+        if (!('addEventListener' in el)) {
             addEventListener = function (element, eventName, callback) {
                 element.attachEvent('on' + eventName, callback);
             };
