Disable the `dropdown button` when it's no children.

Resolve #11785

framework/src/Volo.Abp.AspNetCore.Mvc.UI.Theme.Shared/wwwroot/libs/abp/aspnetcore-mvc-ui-theme-shared/datatables/datatables-extensions.js

@@ -168,12 +168,11 @@ var abp = abp || {};
 
             if ($dropdownItemsContainer.find('li').length > 0) {
                 $dropdownItemsContainer.appendTo($container);
-                $dropdownButton.prependTo($container);
+            } else {
+                $dropdownButton.attr('disabled', 'disabled');
             }
 
-            if ($dropdownItemsContainer.children().length === 0) {
+            $dropdownButton.prependTo($container);
-                return "";
-            }
 
             return $container;
         };