java.lang.IndexOutOfBoundsException: Wrong line: 1. Available lines count: 1

I don't know how to reproduce but by playing with JDTLS I had this error:

java.lang.IndexOutOfBoundsException: Wrong line: 1. Available lines count: 1
	at com.intellij.openapi.editor.impl.LineSet.checkLineIndex(LineSet.java:197)
	at com.intellij.openapi.editor.impl.LineSet.getLineEnd(LineSet.java:191)
	at com.intellij.openapi.editor.impl.DocumentImpl.getLineEndOffset(DocumentImpl.java:1018)
	at com.redhat.devtools.lsp4ij.features.foldingRange.LSPFoldingRangeBuilder.getStartOffset(LSPFoldingRangeBuilder.java:180)
	at com.redhat.devtools.lsp4ij.features.foldingRange.LSPFoldingRangeBuilder.getTextRange(LSPFoldingRangeBuilder.java:151)
	at com.redhat.devtools.lsp4ij.features.foldingRange.LSPFoldingRangeBuilder.getTextRange(LSPFoldingRangeBuilder.java:124)
	at com.redhat.devtools.lsp4ij.features.foldingRange.LSPFoldingRangeBuilder.buildLanguageFoldRegions(LSPFoldingRangeBuilder.java:68)
	at com.intellij.lang.folding.CustomFoldingBuilder.buildFoldRegions(CustomFoldingBuilder.java:43)
	at com.intellij.lang.folding.LanguageFolding.buildFoldingDescriptorsNoPlaceholderCaching(LanguageFolding.java:92)
	at com.intellij.lang.folding.LanguageFolding.buildFoldingDescriptors(LanguageFolding.java:74)
	at com.intellij.codeInsight.folding.impl.FoldingUpdate.getFoldingsFor(FoldingUpdate.java:272)
	at com.intellij.codeInsight.folding.impl.FoldingUpdate.getFoldingsFor(FoldingUpdate.java:240)
	at com.intellij.codeInsight.folding.impl.FoldingUpdate.getUpdateResult(FoldingUpdate.java:89)
	at com.intellij.codeInsight.folding.impl.FoldingUpdate.lambda$updateFoldRegions$0(FoldingUpdate.java:78)
	at com.intellij.psi.impl.PsiCachedValueImpl.doCompute(PsiCachedValueImpl.java:37)
	at com.intellij.util.CachedValueBase.lambda$getValueWithLock$3(CachedValueBase.java:240)
	at com.intellij.util.CachedValueBase.computeData(CachedValueBase.java:43)
	at com.intellij.util.CachedValueBase.lambda$getValueWithLock$4(CachedValueBase.java:240)
	at com.intellij.openapi.util.RecursionManager$1.computePreventingRecursion(RecursionManager.java:110)
	at com.intellij.openapi.util.RecursionGuard.doPreventingRecursion(RecursionGuard.java:27)
	at com.intellij.openapi.util.RecursionManager.doPreventingRecursion(RecursionManager.java:65)
	at com.intellij.util.CachedValueBase.getValueWithLock(CachedValueBase.java:241)
	at com.intellij.psi.impl.PsiCachedValueImpl.getValue(PsiCachedValueImpl.java:27)
	at com.intellij.util.CachedValuesManagerImpl.getCachedValue(CachedValuesManagerImpl.java:69)
	at com.intellij.codeInsight.folding.impl.FoldingUpdate.updateFoldRegions(FoldingUpdate.java:75)
	at com.intellij.codeInsight.folding.impl.CodeFoldingManagerImpl.updateFoldRegions(CodeFoldingManagerImpl.java:231)
	at com.intellij.codeInsight.folding.impl.CodeFoldingManagerImpl.updateFoldRegionsAsync(CodeFoldingManagerImpl.java:217)
	at com.intellij.codeInsight.folding.impl.CodeFoldingPass.doCollectInformation(CodeFoldingPass.java:27)
	at com.intellij.codeHighlighting.TextEditorHighlightingPass.collectInformation(TextEditorHighlightingPass.java:57)
	at com.intellij.codeInsight.daemon.impl.PassExecutorService$ScheduledPass.lambda$doRun$1(PassExecutorService.java:390)
	at com.intellij.platform.diagnostic.telemetry.helpers.TraceKt.runWithSpanIgnoreThrows(trace.kt:77)
	at com.intellij.platform.diagnostic.telemetry.helpers.TraceUtil.runWithSpanThrows(TraceUtil.java:24)
	at com.intellij.codeInsight.daemon.impl.PassExecutorService$ScheduledPass.lambda$doRun$2(PassExecutorService.java:386)
	at com.intellij.openapi.application.impl.ApplicationImpl.tryRunReadAction(ApplicationImpl.java:1133)
	at com.intellij.codeInsight.daemon.impl.PassExecutorService$ScheduledPass.lambda$doRun$3(PassExecutorService.java:377)
	at com.intellij.openapi.progress.impl.CoreProgressManager.lambda$executeProcessUnderProgress$13(CoreProgressManager.java:604)
	at com.intellij.openapi.progress.impl.CoreProgressManager.registerIndicatorAndRun(CoreProgressManager.java:679)
	at com.intellij.openapi.progress.impl.CoreProgressManager.computeUnderProgress(CoreProgressManager.java:635)
	at com.intellij.openapi.progress.impl.CoreProgressManager.executeProcessUnderProgress(CoreProgressManager.java:603)
	at com.intellij.openapi.progress.impl.ProgressManagerImpl.executeProcessUnderProgress(ProgressManagerImpl.java:61)
	at com.intellij.codeInsight.daemon.impl.PassExecutorService$ScheduledPass.doRun(PassExecutorService.java:376)
	at com.intellij.codeInsight.daemon.impl.PassExecutorService$ScheduledPass.lambda$run$0(PassExecutorService.java:352)
	at com.intellij.openapi.application.impl.ReadMostlyRWLock.executeByImpatientReader(ReadMostlyRWLock.java:201)
	at com.intellij.openapi.application.impl.ApplicationImpl.executeByImpatientReader(ApplicationImpl.java:207)
	at com.intellij.codeInsight.daemon.impl.PassExecutorService$ScheduledPass.run(PassExecutorService.java:350)
	at com.intellij.concurrency.JobLauncherImpl$VoidForkJoinTask$1.exec(JobLauncherImpl.java:185)
	at java.base/java.util.concurrent.ForkJoinTask.doExec$$$capture(ForkJoinTask.java:373)
	at java.base/java.util.concurrent.ForkJoinTask.doExec(ForkJoinTask.java)
	at java.base/java.util.concurrent.ForkJoinPool$WorkQueue.topLevelExec(ForkJoinPool.java:1182)
	at java.base/java.util.concurrent.ForkJoinPool.scan(ForkJoinPool.java:1655)
	at java.base/java.util.concurrent.ForkJoinPool.runWorker(ForkJoinPool.java:1622)
	at java.base/java.util.concurrent.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:165)

Start with LSPFoldingRangeBuilder, especially getStartOffset and getTextRange, using the stack trace as the entry point. Investigate how folding ranges are converted to document offsets when the document has one available line; no reproduction or test is provided in the issue. Done means the reported IndexOutOfBoundsException is prevented for this case and folding remains functional.