slideshow.c: Update comment (again)

       * would otherwise fail; it's only executed in the aforementioned case,

       * causing slideshows to exit although there still are lots of working slides.

       *

	  * This warning will remain here for now, in case someone finds circumstances

	  * in which we actually need to exit feh here.

       * So far, there is one known case were we should exit here:

       * When viewing a set of files, externally removing all of them and then resizing

       * the window in feh, feh will print lots of imlib errors and eventually segfault.

       */

      weprintf("No more slides in show?");

   }