Coverage As -> JUnit Test in Eclipse Oxygen reports NullPointerException - eclipse

Question

When I run a JUnit 4 test using Code Coverage from within the Eclipse IDE, All I get is a dialog saying "An internal error occurred during: "Launching AlgebraicNumberTest".
java.lang.NullPointerException"
The same JUnit test runs fine under the debugger or using just plain run or from a gradle command line. Code coverage works fine when running the main application rather than JUnit tests. I just can't get Code Coverage and the JUnit test to work together. They were working together on this project at one point several months ago. I don't know what's changed.
I'm using JUnit 4.12 and Eclipse Oxygen.3a Release (4.7.3a).
* * * UPDATE * * *
I found the Eclipse log file at %USERPROFILE%\eclipse-workspace.metadata.log.
Here's the exception detail from the log file:
!ENTRY org.eclipse.core.jobs 4 2 2018-07-17 20:43:33.964
!MESSAGE An internal error occurred during: "Launching AlgebraicNumberTest".
!STACK 0
java.lang.NullPointerException
at org.eclipse.jdt.junit.launcher.JUnitLaunchConfigurationDelegate.launch(JUnitLaunchConfigurationDelegate.java:204)
at org.eclipse.visualvm.launcher.java.VisualVMJUnitDelegate.launch(VisualVMJUnitDelegate.java:20)
at org.eclipse.eclemma.core.launching.CoverageLauncher.launch(CoverageLauncher.java:94)
at org.eclipse.debug.internal.core.LaunchConfiguration.launch(LaunchConfiguration.java:885)
at org.eclipse.debug.internal.core.LaunchConfiguration.launch(LaunchConfiguration.java:739)
at org.eclipse.debug.internal.ui.DebugUIPlugin.buildAndLaunch(DebugUIPlugin.java:1039)
at org.eclipse.debug.internal.ui.DebugUIPlugin$8.run(DebugUIPlugin.java:1256)
at org.eclipse.core.internal.jobs.Worker.run(Worker.java:56)

Answer 1

I uninstalled the "VisualVM Launcher Feature 1.1.2" plugin as suggested by #Godin. That seems to have resolved the problem that I originally posted.
I plan to eventually reinstall VisualVM. If it causes any problems, I'll post a new question.
Thanks all.