removed bug in get.mpt.fia

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/mptinr@123 edb9625f-4e0d-4859-8d74-9fd3b1da38cb
removed bug in obtaining fia for single datasets via fit.mpt

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/mptinr@124 edb9625f-4e0d-4859-8d74-9fd3b1da38cb