EDS fatal error "No URL return parameter provided"

[Peter Schober]

* Peter Schober <peter.schober at univie.ac.at> [2020-12-07 17:31]:
> FWIW, changing the path to the EDS to
> https://filesender.aco.net/select-institution/
> doesn't change anything.

The URL I'm testing with is this:
https://filesender.aco.net/Shibboleth.sso/Login?target=https%3A%2F%2Ffilesender.aco.net%2F%3Fs%3Dtransfers%23transfer_12345

(You can see also the idpselect_config.js that's in use there.)

After selecting the IDP the request to the SP has the static
defaultReturn value in it as target (which you can also see, even if
you can't access any of the IDPs offered).

(Going with the configured, static, defaultReturn value may be the
intended functionality, even if that's not what "default" means to
me[1], but I can't set it to null otherwise I'll run into the error
message from the subject line of this message. Rock <- me -> hard place.)

-peter

[1] Use if no value provided?