title: How to represent the lack of widget in flutter?
body: <p>I have a container where I want to display border with the condition, If the condition is true then display the border else do not display.</p>
  
  <p>something like this:- </p>
  
  <pre><code>bool condition1;
  bool condition2;
  
  content: Container(
      decoration: BoxDecoration(
        border: Border(
          top: condition1 ? BorderSide(
            color: Colors.grey[300],
            style: BorderStyle.solid,
            width: 1,
          ) : null,
          bottom: condition1 ? BorderSide(
            color: Colors.grey[300],
            style: BorderStyle.solid,
            width: 1,
          ) : null,
        ),
      ),
     child: Container(),
     ),
  </code></pre>
  
  <p>but i cant pass the <code>null</code>, its giving error.</p>
  
  <p>another way I could do is to make width 0.0, but the border does not go completely. so I want to remove the border widget.</p>
  
  <p>so, if we cant use <code>null</code> then how to represent the lack of widget in a flutter.</p>