branch boyceg: added guards to prevent division by zero in IBStandardForceGen in the case of zero-length links
branch boyceg: added guards to prevent division by zero in IBStandardForceGen in the case of zero-length links

huahbo/IBAMR,huahbo/IBAMR,huahbo/IBAMR,iamciera/IBAMR,huahbo/IBAMR,iamciera/IBAMR,yaojieuh/IBAMR,yaojieuh/IBAMR,yaojieuh/IBAMR,huahbo/IBAMR,huahbo/IBAMR,iamciera/IBAMR,iamciera/IBAMR,yaojieuh/IBAMR,yaojieuh/IBAMR,iamciera/IBAMR,yaojieuh/IBAMR,huahbo/IBAMR,iamciera/IBAMR,yaojieuh/IBAMR,iamciera/IBAMR