fix(uiGridMenu): Only run applyHide when not shown

applyHide() was running on all GRID_SCROLL events, whether or not the menu
was visible. This was causing excess $digest() loops.

Author: c0bra

src/js/core/directives/ui-grid-menu.js

@@ -123,9 +123,11 @@ function ($compile, $timeout, $window, $document, gridUtil, uiGridConstants) {
 
     // *** Auto hide when click elsewhere ******
       var applyHideMenu = function(){
-        $scope.$apply(function () {
-          $scope.hideMenu();
-        });
+        if ($scope.shown) {
+          $scope.$apply(function () {
+            $scope.hideMenu();
+          });
+        }
       };
 
       if (typeof($scope.autoHide) === 'undefined' || $scope.autoHide === undefined) {