I am unable to run Jenkins any more. As soon as I try to reach the sever following error is thrown

hudson.util.HudsonFailedToLoad: org.jvnet.hudson.reactor.ReactorException: java.lang.NullPointerException
at hudson.WebAppMain$3.run(WebAppMain.java:237)
Caused by: org.jvnet.hudson.reactor.ReactorException: java.lang.NullPointerException
at org.jvnet.hudson.reactor.Reactor.execute(Reactor.java:269)
at jenkins.InitReactorRunner.run(InitReactorRunner.java:44)
at jenkins.model.Jenkins.executeReactor(Jenkins.java:919)
at jenkins.model.Jenkins.<init>(Jenkins.java:813)
at hudson.model.Hudson.<init>(Hudson.java:83)
at hudson.model.Hudson.<init>(Hudson.java:79)
at hudson.WebAppMain$3.run(WebAppMain.java:225)
Caused by: java.lang.NullPointerException
at com.github.mjdetullio.jenkins.plugins.multibranch.AbstractMultiBranchProject.getACL(AbstractMultiBranchProject.java:1418)
at hudson.model.AbstractItem.hasPermission(AbstractItem.java:506)
at jenkins.model.Jenkins.getItems(Jenkins.java:1369)
at jenkins.model.Jenkins.getItems(Jenkins.java:307)
at hudson.model.Items.getAllItems(Items.java:309)
at hudson.model.Items.getAllItems(Items.java:305)
at jenkins.model.Jenkins.getAllItems(Jenkins.java:1403)
at hudson.model.DependencyGraph.getAllProjects(DependencyGraph.java:151)
at hudson.model.DependencyGraph.build(DependencyGraph.java:94)
at jenkins.model.Jenkins.rebuildDependencyGraph(Jenkins.java:3759)
at jenkins.model.Jenkins$19.run(Jenkins.java:2697)
at org.jvnet.hudson.reactor.TaskGraphBuilder$TaskImpl.run(TaskGraphBuilder.java:169)
at org.jvnet.hudson.reactor.Reactor.runTask(Reactor.java:282)
at jenkins.model.Jenkins$7.runTask(Jenkins.java:903)
at org.jvnet.hudson.reactor.Reactor$2.run(Reactor.java:210)
at org.jvnet.hudson.reactor.Reactor$Node.run(Reactor.java:117)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at java.lang.Thread.run(Thread.java:745)