It seems the same issue like this bug: https://bugzilla.redhat.com/show_bug.cgi?id=1532936.

OK, first, to confirm my recollection, the NPE reported occurs when you click the "manage jenkins" link followed by the "configure system" link.

It occurs prior to trying to click the add environment variables button.

The problem with the add env variable button as it turns out is a known bug in v1.0 and v1.1 of the k8s plugin, namely https://issues.jenkins-ci.org/browse/JENKINS-47112

And per https://issues.jenkins-ci.org/browse/JENKINS-47112 it was fixed with 1.1.3 of the plugin.

As adding env vars is import wrt the original issue, I'm going to use this bug to bump the k8s plugin to 1.1.3

PR https://github.com/openshift/jenkins/pull/622 submitted for 3.7

Note, neither 3.6 or 3.9 of the image have the k8s plugin with the bug for add env vars ... hence why the testing for those release have not / will not hit this.

Also, https://buildvm.openshift.eng.bos.redhat.com:8443/job/devex/job/devex%252Fjenkins-plugins/48/ ran successfully and should update the plugin rpm for the 3.7 rhel7 build, where the k8s plugin is bumped to 1.1.3

Moving to modified ... awaiting arrival of new 3.7 images on brew-pulp

Verified with below version, Add Environment Variables button works now:
brew-pulpxxxxxx/openshift3/jenkins-2-rhel7             v3.7                044c1757df27

Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory, and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

https://access.redhat.com/errata/RHBA-2018:2009