java.lang.AssertionError
        at org.netbeans.modules.languages.yaml.YamlScanner$YamlStructureItem.initializeChildren(YamlScanner.java:284)
        at org.netbeans.modules.languages.yaml.YamlScanner$YamlStructureItem.initializeChildren(YamlScanner.java:340)
        at org.netbeans.modules.languages.yaml.YamlScanner$YamlStructureItem.initializeChildren(YamlScanner.java:340)
        at org.netbeans.modules.languages.yaml.YamlScanner$YamlStructureItem.initializeChildren(YamlScanner.java:340)
        at org.netbeans.modules.languages.yaml.YamlScanner$YamlStructureItem.initializeChildren(YamlScanner.java:340)
        at org.netbeans.modules.languages.yaml.YamlScanner$YamlStructureItem.initializeChildren(YamlScanner.java:340)
        at org.netbeans.modules.languages.yaml.YamlScanner$YamlStructureItem.initialize(YamlScanner.java:212)
        at org.netbeans.modules.languages.yaml.YamlScanner$YamlStructureItem.access$000(YamlScanner.java:151)
        at org.netbeans.modules.languages.yaml.YamlScanner.scanStructure(YamlScanner.java:91)
        at org.netbeans.modules.languages.yaml.YamlParserResult.getItems(YamlParserResult.java:97)
        at org.netbeans.modules.languages.yaml.YamlScanner.folds(YamlScanner.java:103)
        at org.netbeans.modules.csl.editor.fold.GsfFoldManager$JavaElementFoldTask.addTree(GsfFoldManager.java:496)
        at org.netbeans.modules.csl.editor.fold.GsfFoldManager$JavaElementFoldTask.scan(GsfFoldManager.java:492)
        at org.netbeans.modules.csl.editor.fold.GsfFoldManager$JavaElementFoldTask.access$200(GsfFoldManager.java:299)
        at org.netbeans.modules.csl.editor.fold.GsfFoldManager$JavaElementFoldTask$1.run(GsfFoldManager.java:395)
        at org.netbeans.modules.parsing.api.ParserManager$UserTaskAction.run(ParserManager.java:129)
        at org.netbeans.modules.parsing.api.ParserManager$UserTaskAction.run(ParserManager.java:113)
        at org.netbeans.modules.parsing.impl.TaskProcessor.runUserTask(TaskProcessor.java:190)
        at org.netbeans.modules.parsing.api.ParserManager.parse(ParserManager.java:99)
        at org.netbeans.modules.csl.editor.fold.GsfFoldManager$JavaElementFoldTask.gsfFoldScan(GsfFoldManager.java:377)
        at org.netbeans.modules.csl.editor.fold.GsfFoldManager$JavaElementFoldTask.run(GsfFoldManager.java:353)
        at org.netbeans.modules.csl.editor.fold.GsfFoldManager$JavaElementFoldTask.run(GsfFoldManager.java:299)
        at org.netbeans.modules.parsing.impl.TaskProcessor$CompilationJob.run(TaskProcessor.java:654)
        at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:441)
        at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:303)
        at java.util.concurrent.FutureTask.run(FutureTask.java:138)
        at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
        at java.lang.Thread.run(Thread.java:637)