Handle poster only if there is one

Author: bergie

index.coffee

@@ -201,8 +201,8 @@ module.exports = class Flatten
         video =
           type: 'video'
           html: @tagToHtml tag, id
-          src: tag.attribs.poster
         video.video = tag.attribs.src if tag.attribs.src
+        video.src = tag.attribs.poster if tag.attribs.poster
         results.push video
       when 'iframe'
         return results unless tag.attribs