bug symfony#19038 Fix feature detection for IE (Alsciende)

This PR was submitted for the master branch but it was merged into the 2.7 branch instead (closes symfony#19038).

Discussion
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Fix feature detection for IE

| Q             | A
| ------------- | ---
| Branch?       | 2.7
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets |
| License       | MIT
| Doc PR        |

operator `!` has higher precedence (4) than operator `in` (8). Parentheses are mandatory here to have a chance at passing the test.

Commits
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b35658b Fix feature detection for IE

Author: stof

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);
             };