DEV: prevents Pretender Object to leak between tests (#7726)

DEV: prevents Pretender Object to leak between tests (#7726)

diff --git a/test/javascripts/test_helper.js b/test/javascripts/test_helper.js
index 3fdeaae..ee3ee12 100644
--- a/test/javascripts/test_helper.js
+++ b/test/javascripts/test_helper.js
@@ -155,6 +155,8 @@ QUnit.testDone(function() {
 
   server.shutdown();
 
+  window.server = null;
+
   // ensures any event not removed is not leaking between tests
   // most likely in intialisers, other places (controller, component...)
   // should be fixed in code

GitHub sha: fce34aa7