MINOR: Add a fallback thumbnail image for oEmbed inserts

README.md

@@ -39,3 +39,4 @@ and [installation from source](http://doc.silverstripe.org/framework/en/installa
 ## Attribution ##
 
  * Some icons by [Yusuke Kamiyamane](http://p.yusukekamiyamane.com/). All rights reserved. Licensed under a [Creative Commons Attribution 3.0 License](http://creativecommons.org/licenses/by/3.0/).
+ * default_media.png by Thibault Geffroy from [The Noun Project](http://thenounproject.com/). All rights reserved. Licensed under a [Creative Commons Attribution 3.0 License](http://creativecommons.org/licenses/by/3.0/).

forms/HtmlEditorField.php

@@ -553,7 +553,7 @@ class HtmlEditorField_Toolbar extends RequestHandler {
 		} elseif($file->Type == 'photo') {
 			$thumbnailURL = $file->Oembed->url;
 		} else {
-			$thumbnailURL = $url;
+			$thumbnailURL = FRAMEWORK_DIR . '/images/default_media.png';
 		}
 		
 		$previewField = new LiteralField("ImageFull",