fix episode.imageUrl when no cover art is set
fix episode.imageUrl when no cover art is set

podlove/podlove-publisher,noplanman/podlove-publisher,katrinleinweber/podlove-publisher,katrinleinweber/podlove-publisher,noplanman/podlove-publisher,podlove/podlove-publisher,katrinleinweber/podlove-publisher,noplanman/podlove-publisher,katrinleinweber/podlove-publisher,katrinleinweber/podlove-publisher,podlove/podlove-publisher,noplanman/podlove-publisher,podlove/podlove-publisher,podlove/podlove-publisher,podlove/podlove-publisher,noplanman/podlove-publisher