SSDM-3745: bug in Jython25InterpreterFactory fixed

SVN: 36758

common/source/java/ch/systemsx/cisd/common/jython/v25/Jython25InterpreterFactory.java

@@ -153,7 +153,7 @@ public class Jython25InterpreterFactory implements IJythonInterpreterFactory
             try
             {
                 PyFunction function = interpreter.get(name, PyFunction.class);
-                return new Jython25Function(function);
+                return function == null ? null : new Jython25Function(function);
             } catch (Exception e)
             {
                 return null;