Function & Action returning an enum throw an exception during dispatching

    private void handleFunctionDispatching(final ODataRequest request, final ODataResponse response,
            final UriResourceFunction uriResourceFunction) throws ODataApplicationException, ODataLibraryException
    {
        EdmFunction function = uriResourceFunction.getFunction();
        if (function == null)
        {
            function = uriResourceFunction.getFunctionImport().getUnboundFunctions().get(0);
        }
        final EdmReturnType returnType = function.getReturnType();
        switch (returnType.getType().getKind())
        {
            case ENTITY:
                handleEntityDispatching(request, response,
                        returnType.isCollection() && uriResourceFunction.getKeyPredicates().isEmpty(), false);
                break;
            case PRIMITIVE:
            case ENUM:
                handlePrimitiveDispatching(request, response, returnType.isCollection());
                break;
            case COMPLEX:
                handleComplexDispatching(request, response, returnType.isCollection());
                break;
            default:
                throw new ODataHandlerException(NOT_IMPLEMENTED_MESSAGE,
                        ODataHandlerException.MessageKeys.FUNCTIONALITY_NOT_IMPLEMENTED);
        }
    }