title: Set Flutter bottomNavigationBar inactive
body: <p>I'm having an app with a bottom navigation bar: </p>
  
  <pre><code>BottomNavigationBar(
   type: BottomNavigationBarType.fixed,
   items: [
  
     BottomNavigationBarItem(
      icon: Image.asset('assets/icons/inactive/sth.png'),
      activeIcon: Image.asset('assets/icons/active/sth.png'),
      title: Text('Sth')
     ),
  
     BottomNavigationBarItem(
      icon: Image.asset('assets/icons/inactive/sth.png'),
      activeIcon: Image.asset('assets/icons/active/sth.png'),
      title: Text('Sth')
     ),
  
    ],
    onTap: (int index) {
      _currentIndex = index;
    },
    currentIndex: _currentIndex
  )
  </code></pre>
  
  <p>Now I have some use cases where I want to display the bottomNavigationBar but none of its items should be active. </p>
  
  <p>When setting the currentIndex to a non-existing index, I'm getting an error as expected.</p>
  
  <p>Is there any way to achieve my goal?</p>
  
  <p>Thank you in advance.</p>