Fix weekly acceptance broken by r21403 (#2449?)

git-svn-id: https://chaste.cs.ox.ac.uk/svn/chaste/trunk@21533 b5f69653-2bf5-0310-8201-b0dafb8e1405
#2521 Created and tested a FarhadifarForce

git-svn-id: https://chaste.cs.ox.ac.uk/svn/chaste/trunk@21543 b5f69653-2bf5-0310-8201-b0dafb8e1405