title: Check if image asset exists (Flutter)
body: <p>To preface, I have reviewed the post <a href="https://stackoverflow.com/questions/52908923/check-if-asset-exist-in-flutter">here</a>, but am still having trouble.</p>
  <p>I am building a container that is decorated with an image, only if that image exists in the assets/images/ folder. If it does not exist, the container is decorated with a default image instead.</p>
  <p>The image path is formatted string using a variable, image_id, that assumes a String response from an API.</p>
  <p>Here is a code / pseudo-code hybrid of what I'm trying to do...</p>
  <pre><code>Container(
    height: 200,
    width: 300,
    decoration: BoxDecoration(
      image: DecorationImage(
        image: (AssetImage('assets/images/${image_id}.jpg') exists) //pseudo-code here
          ? AssetImage('assets/images/${image_id}.jpg')
          : AssetImage('assets/images/default.jpg'),
        fit: BoxFit.cover,
      ),
    ),
  );
  </code></pre>