Podcast in playlist but not in mediathek

I have a lot of Podcasts in different playlists whitch i cannot play because the location is an url (for example: http://medien.wdr.de/m/1404204816/radio/zeitzeichen/WDR5_Zeitzeichen_20140709_09 20.mp3 ) but the podcast does not exist anymore.

But i cannot delete them because i can see them only in the playlists and not in the mediathek under podcasts.

How cani delete them?