ERROR: Unexpected error in launching a agent. This is probably a bug in Jenkins.
java.lang.NullPointerException
at com.trilead.ssh2.KnownHosts.hostnameMatches(KnownHosts.java:313)
at com.trilead.ssh2.KnownHosts.getAllKnownHostEntries(KnownHosts.java:260)
at com.trilead.ssh2.KnownHosts.recommendHostkeyAlgorithms(KnownHosts.java:504)
at com.trilead.ssh2.KnownHosts.getPreferredServerHostkeyAlgorithmOrder(KnownHosts.java:282)
at hudson.plugins.sshslaves.verifiers.KnownHostsFileKeyVerificationStrategy.getPreferredKeyAlgorithms(KnownHostsFileKeyVerificationStrategy.java:92)
at hudson.plugins.sshslaves.SSHLauncher$2.call(SSHLauncher.java:837)
at hudson.plugins.sshslaves.SSHLauncher$2.call(SSHLauncher.java:833)
at java.util.concurrent.FutureTask.run(FutureTask.java:266)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
at java.lang.Thread.run(Thread.java:748)
 [04/04/19 15:40:41] Launch failed - cleaning up connection

<?xml version='1.1' encoding='UTF-8'?>
<slave>
   <name>agentNullHost</name>
   <description>agent description</description>
   <remoteFS>/home/jenkins</remoteFS>
   <numExecutors>1</numExecutors>
   <mode>NORMAL</mode>
   <retentionStrategy class="hudson.slaves.RetentionStrategy$Always"/>
    <launcher class="hudson.plugins.sshslaves.SSHLauncher" plugin="ssh-slaves@1.29.4">
       <port>22</port>
       <credentialsId>my-credentials</credentialsId>
       <launchTimeoutSeconds>210</launchTimeoutSeconds>
       <maxNumRetries>10</maxNumRetries>
       <retryWaitTime>15</retryWaitTime>
       <sshHostKeyVerificationStrategy class="hudson.plugins.sshslaves.verifiers.NonVerifyingKeyVerificationStrategy"/>
       <tcpNoDelay>true</tcpNoDelay>
  </launcher>
  <label>linux</label>
  <nodeProperties/>
</slave>