java.util.ConcurrentModificationException

[mariusdkm]

Describe the bug

Intellij reports this Fatal Error:

java.util.ConcurrentModificationException
	at java.base/java.util.HashMap$EntrySpliterator.forEachRemaining(HashMap.java:1769)
	at java.base/java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:484)
	at java.base/java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:474)
	at java.base/java.util.stream.ReduceOps$ReduceOp.evaluateSequential(ReduceOps.java:913)
	at java.base/java.util.stream.AbstractPipeline.evaluate(AbstractPipeline.java:234)
	at java.base/java.util.stream.ReferencePipeline.collect(ReferencePipeline.java:578)
	at de.tum.www1.orion.exercise.registry.OrionGlobalExerciseRegistryService.cleanMap(OrionGlobalExerciseRegistryService.java:133)
	at de.tum.www1.orion.exercise.registry.OrionGlobalExerciseRegistryService.cleanup(OrionGlobalExerciseRegistryService.java:125)
	at de.tum.www1.orion.OrionStartupProjectRefreshActivity.runActivity(OrionStartupProjectRefreshActivity.kt:37)
	at com.intellij.ide.startup.impl.StartupManagerImpl.runStartupActivity(StartupManagerImpl.kt:268)
	at com.intellij.ide.startup.impl.StartupManagerImpl.runActivity(StartupManagerImpl.kt:247)
	at com.intellij.ide.startup.impl.StartupManagerImpl.access$runActivity(StartupManagerImpl.kt:59)
	at com.intellij.ide.startup.impl.StartupManagerImpl$runPostStartupActivities$1.accept(StartupManagerImpl.kt:214)
	at com.intellij.ide.startup.impl.StartupManagerImpl$runPostStartupActivities$1.accept(StartupManagerImpl.kt:59)
	at com.intellij.openapi.extensions.impl.ExtensionPointImpl.processWithPluginDescriptor(ExtensionPointImpl.java:293)
	at com.intellij.openapi.extensions.ExtensionPointName.processWithPluginDescriptor(ExtensionPointName.java:156)
	at com.intellij.ide.startup.impl.StartupManagerImpl.runPostStartupActivities(StartupManagerImpl.kt:209)
	at com.intellij.ide.startup.impl.StartupManagerImpl.access$runPostStartupActivities(StartupManagerImpl.kt:59)
	at com.intellij.ide.startup.impl.StartupManagerImpl$projectOpened$3$1.run(StartupManagerImpl.kt:166)
	at com.intellij.openapi.progress.impl.CoreProgressManager.lambda$runProcess$2(CoreProgressManager.java:183)
	at com.intellij.openapi.progress.impl.CoreProgressManager.registerIndicatorAndRun(CoreProgressManager.java:705)
	at com.intellij.openapi.progress.impl.CoreProgressManager.executeProcessUnderProgress(CoreProgressManager.java:647)
	at com.intellij.openapi.progress.impl.ProgressManagerImpl.executeProcessUnderProgress(ProgressManagerImpl.java:63)
	at com.intellij.openapi.progress.impl.CoreProgressManager.runProcess(CoreProgressManager.java:170)
	at com.intellij.openapi.progress.util.BackgroundTaskUtil.runUnderDisposeAwareIndicator(BackgroundTaskUtil.java:270)
	at com.intellij.openapi.progress.util.BackgroundTaskUtil.runUnderDisposeAwareIndicator(BackgroundTaskUtil.java:248)
	at com.intellij.ide.startup.impl.StartupManagerImpl$projectOpened$3.run(StartupManagerImpl.kt:166)
	at java.base/java.util.concurrent.ForkJoinTask$RunnableExecuteAction.exec(ForkJoinTask.java:1426)
	at java.base/java.util.concurrent.ForkJoinTask.doExec(ForkJoinTask.java:290)
	at java.base/java.util.concurrent.ForkJoinPool$WorkQueue.topLevelExec(ForkJoinPool.java:1020)
	at java.base/java.util.concurrent.ForkJoinPool.scan(ForkJoinPool.java:1656)
	at java.base/java.util.concurrent.ForkJoinPool.runWorker(ForkJoinPool.java:1594)
	at java.base/java.util.concurrent.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:183)

To Reproduce

This happens sometimes during indexing.
For ex. when restarting the IDE or installing a new Plugin.
But I can't reproduce this error consistently.

Expected behavior

No Fatal Error happens

Environment

 - OS: MacOs 11.6.3
 - IntelliJ: 2021.2.4 (Ultimate Edition)
 - Orion Version 1.2.0