{{menuItemClasses}} helper not working correctly?

I have a custom menu.hbs file and my bootstrap theme needs a “nav-item” class on each menu item. Then I wanted to be able to use a custom class on each nav-item that I could insert through the Publii dashboard.

<ul class="navbar-nav">

   {{! loop generating a list of menu items}}
   {{#each items}}
      <li {{menuItemClasses "nav-item"}}>

      {{! check if the menu item is a link }}
      {{#if link}}
         <a
            href="{{menuUrl}}"

            {{! check if title attribute exists }}
            {{#if title}}
               title="{{title}}"
            {{/if}}
            {{! /check if title attribute exists }}

            {{! check if target attribute exists }}
            {{#if target}}
               target="{{target}}"
            {{/if}}
            {{! /check if target attribute exists }}

            {{! check if rel attribute exists }}
            {{#if rel}}
               rel="{{rel}}"
            {{/if}}
            {{! /check if rel attribute exists }}

            {{! check if the menu item contains a submenu }}
            {{#if items}}
               aria-haspopup="true"
            {{/if}} class="nav-link">
            {{! /check if the menu item contains a submenu }}

            {{label}}
         
         {{! /check if the menu item is a link }}

      {{else}}
         {{! if the menu item is not a link display a separator }}
         <span
            {{#if title}}
               title="{{title}}"
            {{/if}}
            {{#if items}}
               aria-haspopup="true"
            {{/if}}>
            {{label}}
         </span>
         {{! if the menu item is not a link display a separator }}
      {{/if}}

      {{! check if the menu item contains a submenu }}
      {{#if items}}
         {{> menu}}
      {{/if}}
      {{! check if the menu item contains a submenu }}

   
   {{/each}}
   {{! /loop generating a list of menu items}}