Debug: address gcc warning (and future coverage issue).
Debug: address gcc warning (and future coverage issue).

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