PHP error if there are no additional image sizes

Hi Tobias,

PHP throws an error (actually 2) when I add the Available Sizes column to Media page AND there are no additional image sizes.

I edited the classes/column/media/available-sizes.php file on line 53 to also check if $_wp_additional_image_sizes is not empty and it seems to be solved:

if ( ! empty( $_wp_additional_image_sizes ) && $missing = array_diff( array_keys( $_wp_additional_image_sizes), array_keys( $meta['sizes'] ) ) ) {

A couple of minutes before I was using some additional image sizes and everything was working fine.

I’d appreciate if you add this solution (or a better one if you have it, of course) to next versions.

Thanks for the plugin!

http://ww.wp.xz.cn/plugins/codepress-admin-columns/