Cloning of GeneProduct may create invalid SBML because of missing required attribute `label`

[draeger]

The clone constructor in GeneProduct only calls its superconstructor. In addition, it should also copy all of its attributes, label in particular (which is a required attribute). As of now, cloning gene products results in invalid SBML.

[dyrpsf]

Hi @draeger ,
This issue is now addressed in PR #275.

The root cause was that GeneProduct.clone() delegates to the copy constructor, but the GeneProduct(GeneProduct nsb) constructor only called super(nsb) and did not copy the required label and associatedSpecies fields. As a result, cloned GeneProduct instances could be invalid and lead to malformed SBML.

The fix updates the copy constructor to explicitly copy both fields when they are set:

if (nsb.isSetLabel()) {
    setLabel(nsb.getLabel());
}
if (nsb.isSetAssociatedSpecies()) {
    setAssociatedSpecies(nsb.getAssociatedSpecies());
}

With this change, clone() now produces a fully equivalent GeneProduct, preserving all required metadata and preventing invalid SBML generation.

Once PR #275 is merged, this issue can be safely closed.