505667: ClassCastException in FocusOutlineAction.configureDecorator

Change-Id: Iaf3bb33230fe44a3b3231830a35affc966446f0d
Task-Url: https://bugs.eclipse.org/bugs/show_bug.cgi?id=505667
Signed-off-by: Frank Becker <eclipse@frank-becker.de>
diff --git a/org.eclipse.mylyn.context.ui/src/org/eclipse/mylyn/internal/context/ui/actions/FocusOutlineAction.java b/org.eclipse.mylyn.context.ui/src/org/eclipse/mylyn/internal/context/ui/actions/FocusOutlineAction.java
index eb38b3c..5a18105 100644
--- a/org.eclipse.mylyn.context.ui/src/org/eclipse/mylyn/internal/context/ui/actions/FocusOutlineAction.java
+++ b/org.eclipse.mylyn.context.ui/src/org/eclipse/mylyn/internal/context/ui/actions/FocusOutlineAction.java
@@ -68,7 +68,8 @@
 	 */
 	private void configureDecorator(TreeViewer viewer) {
 		if (viewer != null) {
-			if (!(viewer.getLabelProvider() instanceof DecoratingLabelProvider)) {
+			if ((viewer.getLabelProvider() instanceof ILabelProvider)
+					&& !(viewer.getLabelProvider() instanceof DecoratingLabelProvider)) {
 				viewer.setLabelProvider(new DecoratingLabelProvider((ILabelProvider) viewer.getLabelProvider(),
 						PlatformUI.getWorkbench().getDecoratorManager().getLabelDecorator()));
 			}