Bug 572597 - NPE in CustomizePerspectiveDialog.getToolbarLabel()

Let show the offending element instead of crashing on null.

Change-Id: Ia91125b6a23cf7cbe097b60af2a5e6e01541479b
Signed-off-by: Andrey Loskutov <loskutov@gmx.de>
Reviewed-on: https://git.eclipse.org/r/c/platform/eclipse.platform.ui/+/179975
Reviewed-by: Matthias Becker <ma.becker@sap.com>
Tested-by: Platform Bot <platform-bot@eclipse.org>
diff --git a/bundles/org.eclipse.ui.workbench/Eclipse UI/org/eclipse/ui/internal/dialogs/cpd/CustomizePerspectiveDialog.java b/bundles/org.eclipse.ui.workbench/Eclipse UI/org/eclipse/ui/internal/dialogs/cpd/CustomizePerspectiveDialog.java
index 79d57aa..38e8572 100644
--- a/bundles/org.eclipse.ui.workbench/Eclipse UI/org/eclipse/ui/internal/dialogs/cpd/CustomizePerspectiveDialog.java
+++ b/bundles/org.eclipse.ui.workbench/Eclipse UI/org/eclipse/ui/internal/dialogs/cpd/CustomizePerspectiveDialog.java
@@ -1384,6 +1384,9 @@
 			return toolbarLabel;
 		}
 		String elementId = elt.getElementId();
+		if (elementId == null) {
+			return "Invalid element: " + elt; //$NON-NLS-1$
+		}
 		ActionSetRegistry registry = WorkbenchPlugin.getDefault().getActionSetRegistry();
 		IActionSetDescriptor findActionSet = registry.findActionSet(elementId);
 		if (findActionSet != null) {