It's an NPE when selecting Project >
Clean..., and the fix is very safe (just adds a null check).
platform-ui-dev-admin@xxxxxxxxxxx wrote on 03/23/2004
> Platform UI has updated their map for the 8 p.m. build tonight to
> fix for editors remaining activated when they shouldn't, and for handlers
> following part activation. Only one project has changed:
> + org.eclipse.ui.workbench