Bug 135709 [WorkingSets] Select Working Sets Select All/Deselect All Enablement
If there are no working sets than both buttons should be disabled.
bundles/org.eclipse.ui.ide/src/org/eclipse/ui/internal/ide/dialogs/ResourceWorkingSetPage.java
private void findCheckedResources(List checkedResources,
            IContainer container) {
        IResource[] resources = null;
        try {
            resources = container.members();
        } catch (CoreException ex) {
            handleCoreException(
                    ex,
                    getShell(),
                    IDEWorkbenchMessages.ResourceWorkingSetPage_error,
                    IDEWorkbenchMessages.ResourceWorkingSetPage_error_updateCheckedState);
        }
        for (int i = 0; i < resources.length; i++) {
            if (tree.getGrayed(resources[i])) {
                if (resources[i].isAccessible()) {
					findCheckedResources(checkedResources,
                            (IContainer) resources[i]);
				} else {
					addWorkingSetElements(checkedResources,
                            (IContainer) resources[i]);
				}
            } else if (tree.getChecked(resources[i])) {
                checkedResources.add(resources[i]);
            }
        }
    }
    /**
     * Implements IWorkingSetPage.
     * 
     * @see org.eclipse.ui.dialogs.IWorkingSetPage#finish()