I would expect the normal [caption] shortcode to be inserted in the post if no media credit exists. The previous code was exactly what showed on the html view. Here are screenshots:
The image before inserting into the post, media credit removed:
https://dl.dropboxusercontent.com/u/24274690/1.png
The image inserted in the visual editor:
https://dl.dropboxusercontent.com/u/24274690/2.png
The html view:
https://dl.dropboxusercontent.com/u/24274690/3.png
I have the same problem. Here’s what the output is if the credit field is left blank:
<img class="size-large wp-image-17308" src="http://xxxxxx-600x400.jpg" alt="this should be the caption text " width="600" height="400" /> this should be the caption text
