Generator: small fix in case the initial value variable is not the same as the equation variable.
Generator: small fix in case the initial value variable is not the same as the equation variable.

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