core: Initialize fields before preparing gst pipeline
core: Initialize fields before preparing gst pipeline

jku/rygel,jku/rygel,Tarnyko/rygel,Pelagicore/Media-Manager-Rygel-patched,luisbg/rygel,Pelagicore/Media-Manager-Rygel-patched,GNOME/rygel,Tarnyko/rygel,GNOME/rygel,GNOME/rygel,Pelagicore/Media-Manager-Rygel-patched