Handle unavailable share providers more graceful
Handle unavailable share providers more graceful

If the sharebymail app (or the federatedshareprovider app) are disabled
this kills a lot of stuff. So we should handle a share provider not
begin available a bit more graceful.

Signed-off-by: Roeland Jago Douma <982d370f7dc34a05b4abe8788f899578d515262d@famdouma.nl>

Ardinis/server,pmattern/server,nextcloud/server,Ardinis/server,xx621998xx/server,jbicha/server,xx621998xx/server,pixelipo/server,andreas-p/nextcloud-server,nextcloud/server,pmattern/server,whitekiba/server,jbicha/server,michaelletzgus/nextcloud-server,andreas-p/nextcloud-server,whitekiba/server,michaelletzgus/nextcloud-server,nextcloud/server,whitekiba/server,michaelletzgus/nextcloud-server,nextcloud/server,jbicha/server,xx621998xx/server,michaelletzgus/nextcloud-server,endsguy/server,pixelipo/server,andreas-p/nextcloud-server,andreas-p/nextcloud-server,pmattern/server,jbicha/server,pmattern/server,Ardinis/server,andreas-p/nextcloud-server,endsguy/server,pixelipo/server,endsguy/server,Ardinis/server,xx621998xx/server,endsguy/server,pixelipo/server,jbicha/server,Ardinis/server,whitekiba/server,endsguy/server,pmattern/server,xx621998xx/server,whitekiba/server,pixelipo/server