parameters are propagated only when not null

converter-CellDesigner/src/main/java/lcsb/mapviewer/converter/model/celldesigner/structure/CellDesignerSpecies.java

@@ -483,9 +483,15 @@ public class CellDesignerSpecies<T extends Species> extends CellDesignerElement<
     result.setInitialAmount(initialAmount);
     result.setCharge(charge);
     result.setInitialConcentration(initialConcentration);
-    result.setOnlySubstanceUnits(onlySubstanceUnits);
-    result.setConstant(constant);
-    result.setBoundaryCondition(boundaryCondition);
+    if (onlySubstanceUnits != null) {
+      result.setOnlySubstanceUnits(onlySubstanceUnits);
+    }
+    if (constant != null) {
+      result.setConstant(constant);
+    }
+    if (boundaryCondition != null) {
+      result.setBoundaryCondition(boundaryCondition);
+    }
     result.setSubstanceUnits(substanceUnits);
     result.setHomodimer(homodimer);
     result.setPositionToCompartment(positionToCompartment);