Fix adding None to list of objectUris
Fix adding None to list of objectUris

closes [#SHARE-78]

CenterForOpenScience/scrapi,CenterForOpenScience/scrapi,fabianvf/scrapi,felliott/scrapi,felliott/scrapi,mehanig/scrapi,alexgarciac/scrapi,erinspace/scrapi,mehanig/scrapi,fabianvf/scrapi,erinspace/scrapi