#2371 failing test.

git-svn-id: https://chaste.cs.ox.ac.uk/svn/chaste/trunk@18572 b5f69653-2bf5-0310-8201-b0dafb8e1405
#2371 overcome problem by returning DBL_MAX for the volume of cells that do no have a voronoi elememt associated with them in `MeshBasedCellPopulation`.

git-svn-id: https://chaste.cs.ox.ac.uk/svn/chaste/trunk@18576 b5f69653-2bf5-0310-8201-b0dafb8e1405