SCMManager: createPullRequest() fails behind proxy.

[schnatterer]

Behind nginx the httpResponse by SCMM looks like so for example:

httpResponse header [server:nginx/1.17.10, date:Wed, 24 Mar 2021 20:03:24 GMT, cache-control:no-cache, location:https://my.host/scm/api/v2/pull-requests/fluxv1/gitops/4]

Leading to

java.lang.NullPointerException: Cannot invoke method split() on null object

Because we look up the header like so:

return httpResponse.headers.Location.split("/")[-1]