22 - Warn users when stylsheets are not set

[guikubivan]

Right now if the stylsheets are not set (can happen if plugin is activated globally on wordpress mu), users will never know and will only see the word "error." 

This needs to be detected automatically and the users warned that they need to go to the settings and set the stylesheets or give them the option to set stylsheets to defaults.

Original link: http://code.google.com/p/ipm-wordpress/issues/detail?id=22

[benabus]

Checkout line 1413 of wordpress_slideshow_classes.php to see where the error message is handled. I know this works on the front end, but other than that, has not been tested.

Maybe a good idea to do some additional error handling, but I'm not sure how errors are returned from the xml parser.