title: Error: Property 'isEmpty' cannot be accessed on 'String?' because it is potentially null. Try accessing using ?. instead
body: <p>I am trying to check <code>value</code> using <code>if</code> but the app crash on that line. I am using flutter.</p>
  <pre><code> if (value == null || value.isEmpty || !value.contains('@')) {
            return 'Please enter a valid email.';
          }
  </code></pre>
  <p>getting that
  Error: Property 'isEmpty' cannot be accessed on 'String?' because it is potentially null.
  Try accessing using ?. instead.</p>