Image Sizes & Automatic Handling - Hardcoded href leading to broken images

Image derivatives that are larger than the size of the original image do not get created, they are forwarded back to the original image in the sizes array.

This is leading to a problem when I use one of these custom derivatives in conjunction with the automatic handling for image node thumbnails. The javascript is changing the href of the thumbnail link to point to the custom derivative image file (ie. /files/images/test.full%20width.jpg), regardless of whether it exists or not. Images that are larger than the "full width" derivative work fine, as those images exists, but smaller images are broken. For them only the original and thumbnails are actually created in the file system.

Thanks for the stellar support.