Fix example

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/tm@1353 edb9625f-4e0d-4859-8d74-9fd3b1da38cb
Nullify rather than remove the 'lazy' component if everything is materialized.

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/tm@1354 edb9625f-4e0d-4859-8d74-9fd3b1da38cb