Error while running TestNG

When executed code using TestNg, the cases are successfully executed but observed the below error.
Please review and suggest why I am getting below error

[TestNG] Reporter org.testng.reporters.JUnitReportReporter@5a39699c failed
java.util.ConcurrentModificationException
at java.util.ArrayList$Itr.checkForComodification(Unknown Source)
at java.util.ArrayList$Itr.next(Unknown Source)
at org.testng.reporters.JUnitReportReporter.getNextConfiguration(JUnitReportReporter.java:220)
at org.testng.reporters.JUnitReportReporter.generateReport(JUnitReportReporter.java:105)
at org.testng.TestNG.generateReports(TestNG.java:1175)
at org.testng.TestNG.run(TestNG.java:1102)
at org.testng.remote.AbstractRemoteTestNG.run(AbstractRemoteTestNG.java:132)
at org.testng.remote.RemoteTestNG.initAndRun(RemoteTestNG.java:236)
at org.testng.remote.RemoteTestNG.main(RemoteTestNG.java:81)