Missing Marketing Icon : <p>When trying to submit my app, iTunes Connect says</p>

<blockquote>
  <p>Missing Marketing Icon. iOS Apps must include a 1024x1024px Marketing Icon in PNG format. Apps that do not include the Marketing Icon cannot be submitted for App Review or Beta App Review.</p>
</blockquote>

<p>I do have a 1024x1024px PNG in my submission in iTunes Connect, under <code>General App Information</code> and <code>App Icon</code>. So I guess they want me to add it as an Asset to the bundle, in Xcode. But when I drag and drop my PNG to this <code>Unassigned</code> placeholder, nothing happens.</p>

<p><a href="https://i.stack.imgur.com/SeYI7.png" rel="noreferrer"><img src="https://i.stack.imgur.com/SeYI7.png" alt="Unassigned placeholder for Marketing 1024x PNG"></a></p>

<p>This error started appearing after WWDC 2017 and I installed XCode 9 Beta. This issue is occuring in Version 8.3.1 (8E1000a) too though.</p>
