The C. elegans genome version available for the RNA STAR tool is very old, WS220 (Oct 2010 release). Many changes have been incorporated since then and the latest version (as of now) is WS284 (May 2022 release: Wormbase release WS284 - WormBase : Nematode Information Resource). Can the Galaxy Team please make this genome version available for RNA STAR analysis? Thanks!
the installation of the latest C. elegans genome has been requested to the Galaxy admins. Since it could take a few days, meanwhile I recommend you upload the genome reference to your history and use it from them.