Clear onpopstate handlers after unit tests

Fixes issue when running Karma tests in Firefox.

Signed-off-by: Morris Jobke <hey@morrisjobke.de>

core/js/tests/specHelper.js

@@ -177,6 +177,10 @@ window.isPhantom = /phantom/i.test(navigator.userAgent);
 		delete($.fn.select2);
 
 		ajaxErrorStub.restore();
+
+		// reset pop state handlers
+		OC.Util.History._handlers = [];
+
 	});
 })();