Null pointer exception in an edge case where the SMP returns 404 but with an empty xml response body

[orco]

We recently run into an issue where we do a lookup but the SMP(in this case smp.difi.no) returns an xml header with a commented out body together with HTTP status 404. Curl output follows below. In network.oxalis.vefa.peppol.lookup.reader.MultiReader.parseServiceGroup it results in an NPE with the message:

Cannot invoke "network.oxalis.vefa.peppol.lookup.api.FetcherResponse.getNamespace()" because "response" is null

Not sure if this should be handled by vefa-peppol or in the code that uses vefa-peppol?

`curl -v B-8c30ca3b541456dde1172d2f56b737d3.iso6523-actorid-upis.edelivery.tech.ec.europa.eu/iso6523-actorid-upis::0192:981299108

• About to connect() to B-8c30ca3b541456dde1172d2f56b737d3.iso6523-actorid-upis.edelivery.tech.ec.europa.eu port 80 (#0)
• Trying 51.144.60.163...
• Connected to B-8c30ca3b541456dde1172d2f56b737d3.iso6523-actorid-upis.edelivery.tech.ec.europa.eu (51.144.60.163) port 80 (#0)

  GET /iso6523-actorid-upis::0192:981299108 HTTP/1.1 User-Agent: curl/7.29.0 Host: B-8c30ca3b541456dde1172d2f56b737d3.iso6523-actorid-upis.edelivery.tech.ec.europa.eu Accept: /

  < HTTP/1.1 404 < Date: Tue, 04 Oct 2022 13:38:55 GMT < Content-Type: text/xml;charset=UTF-8 < Content-Length: 313 < Connection: keep-alive < X-Content-Type-Options: nosniff < X-XSS-Protection: 1; mode=block < Cache-Control: no-cache, no-store, max-age=0, must-revalidate < Pragma: no-cache < Expires: 0 < X-Frame-Options: DENY < <?xml version="1.0" encoding="utf-8" ?>