How do I delete a thumbnail from a note?

[Tkendall99 0]

When looking at my notes there is a thumbnail attached to this note: 

However there is no attached image inside the note, so I cant work out how to delete it?? 

[gazumped 9,568]

Hi.  You presumably have a URL in the note and that image may be related.  Is there a problem with just leaving it there?  The rules on thumbnails are to do with the 'smallest large  dimension' of an image - it always seems too much hassle to try to manipulate image sizes to create a preferred choice...