Re-implement code in ContextMenuContent for possible to have mnemonic duplicates

This changeset causes a NPE and needs to be reworked. It seems like this is something MenuItem itself should handle?

@@ -429,8 +428,10 @@
         int index = getLongestLabel();
         itemsContainer.getChildren().clear();
         if (!getItems().isEmpty()) {
- final MenuItem item = getItems().get(index);
- MenuItemContainer menuItemContainer = new MenuItemContainer(item);
+ // We need to strip mnemonic symbols to avoid mnemonic duplicates
+ String itemText = new TextBinding(getItems().get(index).getText()).getText().
+ replaceAll("_", "__").replaceAll("@", "@@");
+ MenuItemContainer menuItemContainer = new MenuItemContainer(new MenuItem(itemText));
             itemsContainer.getChildren().add(menuItemContainer);
         }
     }