#2362 #2363 #2364 #2365 fix memory. There is probably a safer way to construct `NodesOnlyMesh` to avoid this recurring problem. Might make a ticket.

git-svn-id: https://chaste.cs.ox.ac.uk/svn/chaste/trunk@18522 b5f69653-2bf5-0310-8201-b0dafb8e1405