Fix the background color of an inverted menu

Fix the background color of the active pointer in an vertical inverted menu and the color when hovering an active.

It seems to conflict whit the normal menu (non-inverted) and particularly like at the line 417.
I also didn't look if the secondary menu is also affected.

The test code used:

<div class="ui vertical menu pointing inverted">
      <a class="active teal item">
        Inbox
        <div class="ui teal label">1</div>
      </a>
      <a class="item">
        Spam
        <div class="ui label">51</div>
      </a>
      <a class="item">
        Updates
        <div class="ui label">1</div>
      </a>
      <div class="item">
        <div class="ui small icon input">
          <input type="text" placeholder="Search mail...">
          <i class="search icon"></i>
        </div>
      </div>
    </div>