html - Bootstrap navbar汉堡包图标不垂直对齐

我使用带有引导4.1.2的Fluent工具包。
从navbar docs（我想要这个，因为切换开关在打开/关闭时改变了它的图标）我确实采取了第二个例子，从位置部分。然而，汉堡包并不是垂直居中的。我怎么修？
带错误汉堡包的导航栏：

我试着移除，但没用，我被卡住了。

<script src="https://code.jquery.com/jquery-3.3.1.slim.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.14.0/umd/popper.min.js"></script>
<script src="https://stackpath.bootstrapcdn.com/bootstrap/4.1.2/js/bootstrap.min.js"></script>
<script src="https://cdn.jsdelivr.net/gh/nespero/[email protected]/js/fluent-kit.min.js"></script>
<link href="https://stackpath.bootstrapcdn.com/bootstrap/4.1.1/css/bootstrap.min.css" rel="stylesheet"/>
<link href="https://cdn.jsdelivr.net/gh/nespero/[email protected]/css/fluent-kit.min.css" rel="stylesheet"/>

<nav class="navbar navbar-dark bg-dark py-2">
  <strong class="navbar-text">
    Navbar position example
  </strong>
  <button class="btn mi navbar-toggler  shadow-none mt-0" type="button" data-toggle="collapse" data-target="#navbar-position" aria-controls="navbar-position" aria-expanded="false" aria-label="Toggle navigation">
    <span class="sr-only">Toggle navbar submenu</span>
  </button>
  <div class="collapse navbar-collapse" id="navbar-position">
    <ul class="navbar-nav">
      <li class="nav-item active">
        <a class="nav-link" href="#">Home <span class="sr-only">(current)</span></a>
      </li>
      <li class="nav-item">
        <a class="nav-link" href="#">Features</a>
      </li>
      <li class="nav-item">
        <a class="nav-link" href="#">Pricing</a>
      </li>
      <li class="nav-item">
        <a class="nav-link disabled" href="#">Disabled</a>
      </li>
    </ul>
  </div>
</nav>

最佳答案

从.btn

<script src="https://code.jquery.com/jquery-3.3.1.slim.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.14.0/umd/popper.min.js"></script>
<script src="https://stackpath.bootstrapcdn.com/bootstrap/4.1.2/js/bootstrap.min.js"></script>
<script src="https://cdn.jsdelivr.net/gh/nespero/[email protected]/js/fluent-kit.min.js"></script>
<link href="https://stackpath.bootstrapcdn.com/bootstrap/4.1.1/css/bootstrap.min.css" rel="stylesheet"/>
<link href="https://cdn.jsdelivr.net/gh/nespero/[email protected]/css/fluent-kit.min.css" rel="stylesheet"/>

<nav class="navbar navbar-dark bg-dark py-2">
  <strong class="navbar-text">
    Navbar position example
  </strong>
  <button class="mi navbar-toggler  shadow-none mt-0" type="button" data-toggle="collapse" data-target="#navbar-position" aria-controls="navbar-position" aria-expanded="false" aria-label="Toggle navigation">
    <span class="sr-only">Toggle navbar submenu</span>
  </button>
  <div class="collapse navbar-collapse" id="navbar-position">
    <ul class="navbar-nav">
      <li class="nav-item active">
        <a class="nav-link" href="#">Home <span class="sr-only">(current)</span></a>
      </li>
      <li class="nav-item">
        <a class="nav-link" href="#">Features</a>
      </li>
      <li class="nav-item">
        <a class="nav-link" href="#">Pricing</a>
      </li>
      <li class="nav-item">
        <a class="nav-link disabled" href="#">Disabled</a>
      </li>
    </ul>
  </div>
</nav>