imagecache_preset_delete() calls imagecache_preset_flush() with id instead of preset array

While looking into code for a way to check if imagecache preset by a given name exists for my module, I noticed that there is one inconsistent call to imagecache_preset_flush() in imagecache_preset_delete(). Everywhere else imagecache_preset_flush() is called with preset array, but imagecache_preset_delete() calls it with preset id.

There is also a misleading comment on the type of @param in imagecache_preset_flush() that probably is the source of the above bug.