I guess the very first line of the stacktrace is the important one to know
the root issue
at
smartjenkins.SmartJenkinsComputerListener.onConfigurationChange(SmartJenkinsComputerListener.java:41)
which it's related to: https://plugins.jenkins.io/smart-jenkins
My 2 cents
--
You receiv
java.lang.NullPointerException
at
smartjenkins.SmartJenkinsComputerListener.onConfigurationChange(SmartJenkinsComputerListener.java:41)
at
hudson.model.AbstractCIBase.updateComputerList(AbstractCIBase.java:231)
at jenkins.model.Jenkins.updateComputerList(Jenkins.java:154