org.eclipse.core.runtime.AssertionFailedException when editing ftl file

org.eclipse.core.runtime.AssertionFailedException: assertion failed: 
	at org.eclipse.core.runtime.Assert.isTrue(Assert.java:110)
	at org.eclipse.core.runtime.Assert.isTrue(Assert.java:96)
	at org.eclipse.jface.text.Position.setLength(Position.java:185)
	at org.eclipse.jface.text.rules.FastPartitioner.computePartitioning(FastPartitioner.java:634)
	at org.eclipse.jface.text.AbstractDocument.computePartitioning(AbstractDocument.java:1430)
	at org.eclipse.jface.text.TextUtilities.computePartitioning(TextUtilities.java:431)
	at org.eclipse.jface.text.presentation.PresentationReconciler.createPresentation(PresentationReconciler.java:451)
	at org.eclipse.jface.text.presentation.PresentationReconciler.processDamage(PresentationReconciler.java:569)
	at org.eclipse.jface.text.presentation.PresentationReconciler.access$3(PresentationReconciler.java:567)
	at org.eclipse.jface.text.presentation.PresentationReconciler$InternalListener.textChanged(PresentationReconciler.java:227)
	at org.eclipse.jface.text.TextViewer.updateTextListeners(TextViewer.java:2830)
	at org.eclipse.jface.text.TextViewer$VisibleDocumentListener.documentChanged(TextViewer.java:403)
	at org.eclipse.jface.text.AbstractDocument.doFireDocumentChanged2(AbstractDocument.java:769)
	at org.eclipse.jface.text.AbstractDocument.doFireDocumentChanged(AbstractDocument.java:736)
	at org.eclipse.jface.text.AbstractDocument.doFireDocumentChanged(AbstractDocument.java:721)
	at org.eclipse.jface.text.AbstractDocument.fireDocumentChanged(AbstractDocument.java:796)
	at org.eclipse.jface.text.AbstractDocument.replace(AbstractDocument.java:1191)
	at org.eclipse.jface.text.AbstractDocument.replace(AbstractDocument.java:1210)
	at org.eclipse.jface.text.DefaultDocumentAdapter.replaceTextRange(DefaultDocumentAdapter.java:248)
	at org.eclipse.swt.custom.StyledText.modifyContent(StyledText.java:7268)
	at org.eclipse.swt.custom.StyledText.sendKeyEvent(StyledText.java:8111)
	at org.eclipse.swt.custom.StyledText.doBackspace(StyledText.java:2285)
	at org.eclipse.swt.custom.StyledText.invokeAction(StyledText.java:7058)
	at org.eclipse.swt.custom.StyledText.handleKey(StyledText.java:5959)
	at org.eclipse.swt.custom.StyledText.handleKeyDown(StyledText.java:5986)
	at org.eclipse.swt.custom.StyledText$7.handleEvent(StyledText.java:5663)
	at org.eclipse.swt.widgets.EventTable.sendEvent(EventTable.java:84)
	at org.eclipse.swt.widgets.Display.sendEvent(Display.java:4486)
	at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1388)
	at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1412)
	at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1397)
	at org.eclipse.swt.widgets.Widget.sendKeyEvent(Widget.java:1424)
	at org.eclipse.swt.widgets.Widget.gtk_key_press_event(Widget.java:824)
	at org.eclipse.swt.widgets.Control.gtk_key_press_event(Control.java:3269)
	at org.eclipse.swt.widgets.Composite.gtk_key_press_event(Composite.java:777)
	at org.eclipse.swt.widgets.Widget.windowProc(Widget.java:2098)
	at org.eclipse.swt.widgets.Control.windowProc(Control.java:5510)
	at org.eclipse.swt.widgets.Display.windowProc(Display.java:4700)
	at org.eclipse.swt.internal.gtk.OS._gtk_main_do_event(Native Method)
	at org.eclipse.swt.internal.gtk.OS.gtk_main_do_event(OS.java:9074)
	at org.eclipse.swt.widgets.Display.eventProc(Display.java:1253)
	at org.eclipse.swt.internal.gtk.OS._g_main_context_iteration(Native Method)
	at org.eclipse.swt.internal.gtk.OS.g_main_context_iteration(OS.java:2473)
	at org.eclipse.swt.widgets.Display.readAndDispatch(Display.java:3439)
	at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine$9.run(PartRenderingEngine.java:1151)
	at org.eclipse.core.databinding.observable.Realm.runWithDefault(Realm.java:332)
	at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.run(PartRenderingEngine.java:1032)
	at org.eclipse.e4.ui.internal.workbench.E4Workbench.createAndRunUI(E4Workbench.java:148)
	at org.eclipse.ui.internal.Workbench$5.run(Workbench.java:636)
	at org.eclipse.core.databinding.observable.Realm.runWithDefault(Realm.java:332)
	at org.eclipse.ui.internal.Workbench.createAndRunWorkbench(Workbench.java:579)
	at org.eclipse.ui.PlatformUI.createAndRunWorkbench(PlatformUI.java:150)
	at org.eclipse.ui.internal.ide.application.IDEApplication.start(IDEApplication.java:135)
	at org.eclipse.equinox.internal.app.EclipseAppHandle.run(EclipseAppHandle.java:196)
	at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.runApplication(EclipseAppLauncher.java:134)
	at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.start(EclipseAppLauncher.java:104)
	at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:382)
	at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:236)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:483)
	at org.eclipse.equinox.launcher.Main.invokeFramework(Main.java:648)
	at org.eclipse.equinox.launcher.Main.basicRun(Main.java:603)
	at org.eclipse.equinox.launcher.Main.run(Main.java:1465)
	at org.eclipse.equinox.launcher.Main.main(Main.java:1438)