Bug 528133 - initialize selection to EMPTY, do not return null

Change-Id: Ia63b98d936bbfc79b7ed0466ab8b4a56bd238185
Signed-off-by: Andrey Loskutov <loskutov@gmx.de>
diff --git a/ui/org.eclipse.pde.ui/src/org/eclipse/pde/internal/ui/editor/PDEMultiPageContentOutline.java b/ui/org.eclipse.pde.ui/src/org/eclipse/pde/internal/ui/editor/PDEMultiPageContentOutline.java
index 00aeb7b..a70fc7e 100644
--- a/ui/org.eclipse.pde.ui/src/org/eclipse/pde/internal/ui/editor/PDEMultiPageContentOutline.java
+++ b/ui/org.eclipse.pde.ui/src/org/eclipse/pde/internal/ui/editor/PDEMultiPageContentOutline.java
@@ -38,6 +38,7 @@
 	public PDEMultiPageContentOutline(PDEFormEditor editor) {
 		this.editor = editor;
 		listeners = new ArrayList<>();
+		selection = StructuredSelection.EMPTY;
 		sortingOn = PDEPlugin.getDefault().getPreferenceStore().getBoolean("PDEMultiPageContentOutline.SortingAction.isChecked"); //$NON-NLS-1$
 
 	}