When the "properties" element isn't specified in the JSON form blob the Job processing logic hits a NPE.

This could happen if a Custom project type uses a form that overrides Job's configure.jelly, or if another tool is used to produce the JSON message.

FWIW, I manipulated the JSON message to drop every other field without a problem processing the forms for FreeStyleProject and MatrixProject, "properties" was the only one I couldn't remove and have it do the right thing.

I have a PR to fix this here: https://jenkins.ci.cloudbees.com/job/core/job/jenkins-core/891/