Fixed NPE for the cases when SignatureProductionPlace data is not provided.
Fixed NPE for the cases when SignatureProductionPlace data is not provided.

We must check for null, because SignatureProductionPlace element is OPTIONAL according to the XAdES specification.

keijokapp/digidoc4j,open-eid/digidoc4j,open-eid/digidoc4j,keijokapp/digidoc4j,open-eid/digidoc4j