Fixed TypeError caused by #1904.
Fixed TypeError caused by #1904.

"Resource.relationList is undefinded" after activating a slide.

jwinzer/OpenSlides,ostcar/OpenSlides,boehlke/OpenSlides,OpenSlides/OpenSlides,jwinzer/OpenSlides,normanjaeckel/OpenSlides,jwinzer/OpenSlides,CatoTH/OpenSlides,rolandgeider/OpenSlides,tsiegleauq/OpenSlides,FinnStutzenstein/OpenSlides,rolandgeider/OpenSlides,boehlke/OpenSlides,emanuelschuetze/OpenSlides,rolandgeider/OpenSlides,FinnStutzenstein/OpenSlides,tsiegleauq/OpenSlides,emanuelschuetze/OpenSlides,boehlke/OpenSlides,CatoTH/OpenSlides,OpenSlides/OpenSlides,FinnStutzenstein/OpenSlides,CatoTH/OpenSlides,normanjaeckel/OpenSlides,FinnStutzenstein/OpenSlides,ostcar/OpenSlides,ostcar/OpenSlides,jwinzer/OpenSlides,boehlke/OpenSlides,normanjaeckel/OpenSlides,CatoTH/OpenSlides,emanuelschuetze/OpenSlides,tsiegleauq/OpenSlides,jwinzer/OpenSlides,emanuelschuetze/OpenSlides,normanjaeckel/OpenSlides