Fix Shannon cytosolic sodium metadata, good spot Pras!

git-svn-id: https://chaste.cs.ox.ac.uk/svn/chaste/trunk@18536 b5f69653-2bf5-0310-8201-b0dafb8e1405
Fix memory leak

git-svn-id: https://chaste.cs.ox.ac.uk/svn/chaste/trunk@18537 b5f69653-2bf5-0310-8201-b0dafb8e1405