image_caption unable to remove class from figure element.

When an image is given a caption through the "image_caption" feature you can add custom classes to the figure element via the "style_formats" dropdown but you cannot remove them.

I've set up a fiddle here: http://fiddle.tinymce.com/0ggaab/11

1.) Insert an image with the "Show caption" option selected.
2.) Select FIGURE > FIGCAPTION and apply the Align Left style from the dropdown. (Selecting figure does nothing even though the selector for that style is figure)
3.) If you view the source you can see the "align-left" class is added to the figure element as expected. You can also see it marked as applied in the style_format dropdown.
4.) Go to the dropdown and try to remove the class, nothing happens.

If you go into the source and remove both the image and align-left classes then hit save, you can add and remove the Align Left style via the dropdown with no issues.

Start by reproducing the behavior in the linked TinyMCE fiddle, focusing on the image_caption feature and the style_formats dropdown with figure and figcaption selected. Trace how the Align Left style is applied to the figure and verify that choosing it again or removing it also removes align-left while preserving the caption; no repository file or test is named in the issue.