Fix for bottom variable NaN bug in code
Fix for bottom variable NaN bug in code

nickerso/libcellml,cellml/libcellml,hsorby/libcellml,cellml/libcellml,hsorby/libcellml,nickerso/libcellml,nickerso/libcellml,hsorby/libcellml,cellml/libcellml,cellml/libcellml,nickerso/libcellml,hsorby/libcellml