We occasionaly experience failed git checkouts when an InterruptedException is raised to abort a job. This causes a job to have the result FAILURE instead of ABORTED. 

InterruptedException doesn't have a message and the code in CliGitAPIImpl accesses the message without null check. Two example stack traces (line numbers originate from plugin build from https://github.com/jenkinsci/git-client-plugin/pull/1103, git-client:4.6.1-rc3518.4c581ea_f4c3d):

ERROR: Checkout failed
java.lang.NullPointerException
at org.jenkinsci.plugins.gitclient.CliGitAPIImpl.launchCommandIn(CliGitAPIImpl.java:2852)
at org.jenkinsci.plugins.gitclient.CliGitAPIImpl.launchCommandWithCredentials(CliGitAPIImpl.java:2185)
at org.jenkinsci.plugins.gitclient.CliGitAPIImpl$1.execute(CliGitAPIImpl.java:635)
at org.jenkinsci.plugins.gitclient.CliGitAPIImpl$2.execute(CliGitAPIImpl.java:871)
at hudson.plugins.git.GitSCM.retrieveChanges(GitSCM.java:1222)
at hudson.plugins.git.GitSCM.checkout(GitSCM.java:1305)
at org.jenkinsci.plugins.workflow.steps.scm.SCMStep.checkout(SCMStep.java:129)
at org.jenkinsci.plugins.workflow.cps.CpsScmFlowDefinition.create(CpsScmFlowDefinition.java:165)
at org.jenkinsci.plugins.workflow.cps.CpsScmFlowDefinition.create(CpsScmFlowDefinition.java:71)
at org.jenkinsci.plugins.workflow.job.WorkflowRun.run(WorkflowRun.java:311)
at hudson.model.ResourceController.execute(ResourceController.java:101)
at hudson.model.Executor.run(Executor.java:442)
ERROR: Maximum checkout retry attempts reached, aborting
Finished: FAILURE

ERROR: Checkout failed
java.lang.NullPointerException
at org.jenkinsci.plugins.gitclient.CliGitAPIImpl.launchCommandIn(CliGitAPIImpl.java:2852)
at org.jenkinsci.plugins.gitclient.CliGitAPIImpl.launchCommandIn(CliGitAPIImpl.java:2766)
at org.jenkinsci.plugins.gitclient.CliGitAPIImpl.launchCommandIn(CliGitAPIImpl.java:2761)
at org.jenkinsci.plugins.gitclient.CliGitAPIImpl.launchCommand(CliGitAPIImpl.java:2051)
at org.jenkinsci.plugins.gitclient.CliGitAPIImpl.launchCommand(CliGitAPIImpl.java:2063)
at org.jenkinsci.plugins.gitclient.CliGitAPIImpl.revParse(CliGitAPIImpl.java:1115)
at hudson.plugins.git.GitAPI.revParse(GitAPI.java:419)
at hudson.plugins.git.util.DefaultBuildChooser.getCandidateRevisions(DefaultBuildChooser.java:60)
at hudson.plugins.git.GitSCM.determineRevisionToBuild(GitSCM.java:1148)
at hudson.plugins.git.GitSCM.checkout(GitSCM.java:1306)
at org.jenkinsci.plugins.workflow.steps.scm.SCMStep.checkout(SCMStep.java:129)
at org.jenkinsci.plugins.workflow.cps.CpsScmFlowDefinition.create(CpsScmFlowDefinition.java:165)
at org.jenkinsci.plugins.workflow.cps.CpsScmFlowDefinition.create(CpsScmFlowDefinition.java:71)
at org.jenkinsci.plugins.workflow.job.WorkflowRun.run(WorkflowRun.java:311)
at hudson.model.ResourceController.execute(ResourceController.java:101)
at hudson.model.Executor.run(Executor.java:442)
ERROR: Maximum checkout retry attempts reached, aborting
Finished: FAILURE

Caused by this code section:

} catch (GitException | InterruptedException e) {
    if (e.getMessage().contains("unsupported option \"accept-new\"")) { // causing NPE if getMessage() returns null
        listener.getLogger().println(HyperlinkNote.encodeTo("https://plugins.jenkins.io/git-client/#plugin-content-ssh-host-key-                     verification","If you are using OpenSSH < 7.6 please choose another strategy to verify ssh host key in 'Manage Jenkins' -> 'Configure Global Security' -> 'Git Host Key Verification Configuration'"));}throw e;