This is introduced from 8.0 b75. In Japanese and Korean languages, the HTMLEditor UI got blank, with StringIndexOutOfBoundsException thrown. It looks similar to RT-27199, but this time HTMLEditor is totally unusable in Japanese and Korean languages.

java.lang.StringIndexOutOfBoundsException: String index out of range: -1
at java.lang.String.substring(String.java:1911)
at com.sun.javafx.scene.web.skin.HTMLEditorSkin$14$1.updateItem(HTMLEditorSkin.java:661)
at com.sun.javafx.scene.web.skin.HTMLEditorSkin$14$1.updateItem(HTMLEditorSkin.java:656)
at javafx.scene.control.ListCell.updateItem(ListCell.java:417)
at javafx.scene.control.ListCell.indexChanged(ListCell.java:305)
at javafx.scene.control.IndexedCell.updateIndex(IndexedCell.java:114)
at com.sun.javafx.scene.control.skin.VirtualFlow.setCellIndex(VirtualFlow.java:1559)
at com.sun.javafx.scene.control.skin.VirtualFlow.getCell(VirtualFlow.java:1460)
at com.sun.javafx.scene.control.skin.VirtualFlow.getCellBreadth(VirtualFlow.java:1494)
at com.sun.javafx.scene.control.skin.VirtualFlow.getMaxCellWidth(VirtualFlow.java:1987)
at com.sun.javafx.scene.control.skin.VirtualContainerBase.getMaxCellWidth(VirtualContainerBase.java:92)
at com.sun.javafx.scene.control.skin.ComboBoxListViewSkin$6.computePrefWidth(ComboBoxListViewSkin.java:516)
at javafx.scene.Parent.prefWidth(Parent.java:863)
at javafx.scene.layout.Region.prefWidth(Region.java:1153)
at com.sun.javafx.scene.control.skin.ComboBoxListViewSkin.computePrefWidth(ComboBoxListViewSkin.java:272)
at javafx.scene.control.Control.computePrefWidth(Control.java:457)
at javafx.scene.Parent.prefWidth(Parent.java:863)
at javafx.scene.layout.Region.prefWidth(Region.java:1153)
at javafx.scene.layout.Region.computeChildPrefAreaWidth(Region.java:1372)
at javafx.scene.layout.HBox.getAreaWidths(HBox.java:440)
at javafx.scene.layout.HBox.layoutChildren(HBox.java:539)
at javafx.scene.Parent.layout(Parent.java:1014)
at javafx.scene.Parent.layout(Parent.java:1022)
at javafx.scene.Parent.layout(Parent.java:1022)
at javafx.scene.Parent.layout(Parent.java:1022)
at javafx.scene.Parent.layout(Parent.java:1022)
at javafx.scene.Parent.layout(Parent.java:1022)
at javafx.scene.Scene.layoutDirtyRoots(Scene.java:535)
at javafx.scene.Scene.doLayoutPass(Scene.java:506)
at javafx.scene.Scene.access$4000(Scene.java:178)
at javafx.scene.Scene$ScenePulseListener.pulse(Scene.java:2195)
at com.sun.javafx.tk.Toolkit.firePulse(Toolkit.java:346)
at com.sun.javafx.tk.quantum.QuantumToolkit.pulse(QuantumToolkit.java:525)
at com.sun.javafx.tk.quantum.QuantumToolkit$12.run(QuantumToolkit.java:378)
at com.sun.glass.ui.InvokeLaterDispatcher$Future.run(Unknown Source)
at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
at com.sun.glass.ui.win.WinApplication.access$300(Unknown Source)
at com.sun.glass.ui.win.WinApplication$3$1.run(Unknown Source)
at java.lang.Thread.run(Thread.java:722)