Change Image button dismisses the default IWP icon, but the default icon is used anyways

1. Create a custom plugin
2. Click on `change image` to see the new image upload field
3. don't upload an image
4. submit app

App still has the default image even though the user might have (unsuccessfully) tried to upload a custom image. Maybe this field should be validated? Or the drag-drop field can be the default icon, indicating that the default icon will be used if the user does not take action otherwise.