better handling of missing wd in percentile Rose

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/openair@847 edb9625f-4e0d-4859-8d74-9fd3b1da38cb
more percentileRose fixes

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/openair@848 edb9625f-4e0d-4859-8d74-9fd3b1da38cb