Tidy up of updateBaseUnitCount function.
Tidy up of updateBaseUnitCount function.

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