Youtube embed results in large space below editor

[Nathan Explosion]

Pretty sure I reported this a good while back, on an earlier version of IPS 4 - but it's back on 4.5

Steps to reproduce (tested on Firefox & Chrome)

1. Create a new topic or a reply
2. Paste an embeddable Youtube link (e.g. https://www.youtube.com/watch?v=URJH3ZJzxB0)
3. After it embeds, look below the attachment section of the editor

Result:

1.