Okay... so I'm trying to check to see if a field (thumbnail) is empty. If it is I want it to display the youtube thumbnail. I'm getting an error with this:

{{ if thumbnail }}
      <img class="snapshot" src="{{ thumbnail }}">
      {{ elseif }}
      <div class="video-container">
        <div class="iframe-container">
          <iframe src="{{ youtube_link | embed_url }}" ...></iframe>
        </div>
      </div>
      {{ /if }}

am I missing something?