Fix clang errors in characterBreakdown.
Fix clang errors in characterBreakdown.

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