IndexNotReadyException - index accessed before ready

[jankal]

The following exception appeared while indexing a project:

com.intellij.openapi.project.IndexNotReadyException: Please change caller according to com.intellij.openapi.project.IndexNotReadyException documentation. Dumb mode start trace is in attachment.
	at com.intellij.openapi.project.IndexNotReadyException.create(IndexNotReadyException.java:69)
	at com.intellij.util.indexing.FileBasedIndexImpl.handleDumbMode(FileBasedIndexImpl.java:887)
	at com.intellij.util.indexing.FileBasedIndexImpl.ensureUpToDate(FileBasedIndexImpl.java:835)
	at com.intellij.util.indexing.FileBasedIndexEx.processAllKeys(FileBasedIndexEx.java:181)
	at com.intellij.util.indexing.FileBasedIndexImpl.processAllKeys(FileBasedIndexImpl.java:882)
	at com.intellij.util.indexing.FileBasedIndexEx.processAllKeys(FileBasedIndexEx.java:167)
	at com.intellij.util.indexing.FileBasedIndexEx.getAllKeys(FileBasedIndexEx.java:161)
	at de.shyim.shopware6.xml.AdminComponentProvider.getDescriptor(AdminComponentProvider.kt:40)
	at com.intellij.psi.impl.source.xml.XmlTagDelegate.computeElementDescriptor(XmlTagDelegate.java:455)
	at com.intellij.openapi.util.RecursionManager$1.computePreventingRecursion(RecursionManager.java:113)
	at com.intellij.openapi.util.RecursionGuard.doPreventingRecursion(RecursionGuard.java:29)
	at com.intellij.openapi.util.RecursionManager.doPreventingRecursion(RecursionManager.java:68)
	at com.intellij.psi.impl.source.xml.XmlTagDelegate$1.compute(XmlTagDelegate.java:436)
	at com.intellij.psi.util.CachedValuesManager$1.compute(CachedValuesManager.java:173)
	at com.intellij.psi.impl.AbstractPsiCachedValue.doCompute(PsiCachedValueImpl.kt:21)
	at com.intellij.util.CachedValueBase.lambda$getValueWithLock$3(CachedValueBase.java:299)
	at com.intellij.util.CachedValueBase.computeData(CachedValueBase.java:37)
	at com.intellij.util.CachedValueBase.lambda$getValueWithLock$4(CachedValueBase.java:299)
	at com.intellij.openapi.util.RecursionManager$1.computePreventingRecursion(RecursionManager.java:113)
	at com.intellij.openapi.util.RecursionGuard.doPreventingRecursion(RecursionGuard.java:29)
	at com.intellij.openapi.util.RecursionManager.doPreventingRecursion(RecursionManager.java:68)
	at com.intellij.util.CachedValueBase.getValueWithLock(CachedValueBase.java:300)
	at com.intellij.psi.impl.PsiCachedValueImpl$Direct.getValue(PsiCachedValueImpl.kt:121)
	at com.intellij.util.CachedValuesManagerImpl.getCachedValue(CachedValuesManagerImpl.java:83)
	at com.intellij.psi.util.CachedValuesManager.getCachedValue(CachedValuesManager.java:170)
	at com.intellij.psi.util.CachedValuesManager.getCachedValue(CachedValuesManager.java:136)
	at com.intellij.psi.impl.source.xml.XmlTagDelegate.getDescriptor(XmlTagDelegate.java:432)
	at com.intellij.psi.impl.source.xml.XmlTagImpl.getDescriptor(XmlTagImpl.java:120)
	at com.intellij.codeInsight.completion.HtmlCompletionContributor.addSpecificCompletions(HtmlCompletionContributor.java:111)
	at com.intellij.spellchecker.xml.HtmlSpellcheckingStrategy.getTokenizer(HtmlSpellcheckingStrategy.java:37)
	at com.intellij.spellchecker.tokenizer.SpellcheckingStrategy.getTokenizer(SpellcheckingStrategy.java:58)
	at com.intellij.spellchecker.inspections.SpellCheckingInspection.tokenize(SpellCheckingInspection.java:139)
	at com.intellij.spellchecker.inspections.SpellCheckingInspection.tokenize(SpellCheckingInspection.java:135)
	at com.intellij.spellchecker.inspections.SpellCheckingInspection$1.visitElement(SpellCheckingInspection.java:105)
	at com.intellij.psi.impl.source.xml.XmlAttributeValueImpl.accept(XmlAttributeValueImpl.java:47)
	at com.intellij.codeInsight.daemon.impl.InspectionRunner$InspectionProblemHolder.visitElement(InspectionRunner.java:577)
	at com.intellij.codeInsight.daemon.impl.InspectionRunner.lambda$processContext$18(InspectionRunner.java:404)
	at com.intellij.codeInsight.daemon.impl.InspectionVisitorOptimizer.acceptElements(InspectionVisitorOptimizer.java:200)
	at com.intellij.codeInsight.daemon.impl.InspectionRunner.processContext(InspectionRunner.java:402)
	at com.intellij.codeInsight.daemon.impl.InspectionRunner.lambda$inspect$7(InspectionRunner.java:177)
	at com.intellij.openapi.application.impl.AnyThreadWriteThreadingSupport.tryRunReadAction(AnyThreadWriteThreadingSupport.kt:333)
	at com.intellij.openapi.application.impl.ApplicationImpl.tryRunReadAction(ApplicationImpl.java:971)
	at com.intellij.codeInsight.daemon.impl.InspectionRunner.lambda$executeInImpatientReadAction$14(InspectionRunner.java:377)
	at com.intellij.openapi.application.impl.AnyThreadWriteThreadingSupport.executeByImpatientReader(AnyThreadWriteThreadingSupport.kt:544)
	at com.intellij.openapi.application.impl.ApplicationImpl.executeByImpatientReader(ApplicationImpl.java:176)
	at com.intellij.codeInsight.daemon.impl.InspectionRunner.lambda$executeInImpatientReadAction$15(InspectionRunner.java:376)
	at com.intellij.util.AstLoadingFilter.forceAllowTreeLoading(AstLoadingFilter.java:158)
	at com.intellij.util.AstLoadingFilter.forceAllowTreeLoading(AstLoadingFilter.java:150)
	at com.intellij.codeInsight.daemon.impl.InspectionRunner.lambda$executeInImpatientReadAction$16(InspectionRunner.java:374)
	at com.intellij.util.AstLoadingFilter.disallowTreeLoading(AstLoadingFilter.java:129)
	at com.intellij.util.AstLoadingFilter.disallowTreeLoading(AstLoadingFilter.java:118)
	at com.intellij.codeInsight.daemon.impl.InspectionRunner.executeInImpatientReadAction(InspectionRunner.java:374)
	at com.intellij.codeInsight.daemon.impl.InspectionRunner.lambda$inspect$8(InspectionRunner.java:171)
	at com.intellij.concurrency.ApplierCompleter.processArrayItem(ApplierCompleter.java:126)
	at com.intellij.concurrency.ApplierCompleter.processArray(ApplierCompleter.java:207)
	at com.intellij.concurrency.ApplierCompleter.execAll(ApplierCompleter.java:176)
	at com.intellij.concurrency.ApplierCompleter.lambda$exec$0(ApplierCompleter.java:115)
	at com.intellij.openapi.application.impl.AnyThreadWriteThreadingSupport.tryRunReadAction(AnyThreadWriteThreadingSupport.kt:351)
	at com.intellij.openapi.application.impl.ApplicationImpl.tryRunReadAction(ApplicationImpl.java:971)
	at com.intellij.concurrency.ApplierCompleter.lambda$wrapInReadActionAndIndicator$2(ApplierCompleter.java:158)
	at com.intellij.openapi.progress.impl.CoreProgressManager.lambda$executeProcessUnderProgress$14(CoreProgressManager.java:674)
	at com.intellij.openapi.progress.impl.CoreProgressManager.registerIndicatorAndRun(CoreProgressManager.java:749)
	at com.intellij.openapi.progress.impl.CoreProgressManager.computeUnderProgress(CoreProgressManager.java:705)
	at com.intellij.openapi.progress.impl.CoreProgressManager.executeProcessUnderProgress(CoreProgressManager.java:673)
	at com.intellij.openapi.progress.impl.ProgressManagerImpl.executeProcessUnderProgress(ProgressManagerImpl.java:79)
	at com.intellij.concurrency.ApplierCompleter.wrapInReadActionAndIndicator(ApplierCompleter.java:169)
	at com.intellij.concurrency.ApplierCompleter.lambda$wrapAndRun$1(ApplierCompleter.java:150)
	at com.intellij.openapi.application.impl.AnyThreadWriteThreadingSupport.executeByImpatientReader(AnyThreadWriteThreadingSupport.kt:544)
	at com.intellij.openapi.application.impl.ApplicationImpl.executeByImpatientReader(ApplicationImpl.java:176)
	at com.intellij.concurrency.ApplierCompleter.wrapAndRun(ApplierCompleter.java:150)
	at com.intellij.concurrency.ApplierCompleter.exec(ApplierCompleter.java:118)
	at java.base/java.util.concurrent.ForkJoinTask.doExec(ForkJoinTask.java:507)
	at java.base/java.util.concurrent.ForkJoinPool$WorkQueue.topLevelExec(ForkJoinPool.java:1491)
	at java.base/java.util.concurrent.ForkJoinPool.scan(ForkJoinPool.java:2073)
	at java.base/java.util.concurrent.ForkJoinPool.runWorker(ForkJoinPool.java:2035)
	at java.base/java.util.concurrent.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:187)