After update this plugin some jobs was failed with this error
FATAL: Null value not allowed as an environment variable: gitlabUserEmail
java.lang.IllegalArgumentException: Null value not allowed as an environment variable: gitlabUserEmail
at hudson.EnvVars.put(EnvVars.java:356)
at hudson.model.StringParameterValue.buildEnvironment(StringParameterValue.java:56)
at hudson.model.ParametersAction.buildEnvVars(ParametersAction.java:89)
at hudson.model.AbstractBuild.getEnvironment(AbstractBuild.java:950)
at hudson.plugins.git.GitSCM.checkout(GitSCM.java:1046)
at hudson.scm.SCM.checkout(SCM.java:485)
at hudson.model.AbstractProject.checkout(AbstractProject.java:1276)
at hudson.model.AbstractBuild$AbstractBuildExecution.defaultCheckout(AbstractBuild.java:607)
at jenkins.scm.SCMCheckoutStrategy.checkout(SCMCheckoutStrategy.java:86)
at hudson.model.AbstractBuild$AbstractBuildExecution.run(AbstractBuild.java:529)
at hudson.model.Run.execute(Run.java:1738)
at hudson.model.FreeStyleBuild.run(FreeStyleBuild.java:43)
at hudson.model.ResourceController.execute(ResourceController.java:98)
at hudson.model.Executor.run(Executor.java:410)

Downgrade to v1.1.28