Error when trying to price instrument when using Quantlib

Question

I am receiving the following error when trying to price a 20x10 swap from a bootstrapped curve. The error get thrown on the last line of the ImpliedRate function

SwapRatesServiceTests.ImpliedRate_ForTwenty_x_TenYearSwap_ReturnsRate: System.ApplicationException : 2nd leg: empty Handle cannot be dereferenced

I don't have the faintest idea where to start to debug this issue. Any assistance will be highly appreciated.

IMPORTANT: I am using the C# Swig version of Quantlib, so my actual prod code is as follows based on the swapvaluation.cpp example:

The test method:

    [Test]
    public void ImpliedRate_ForTwenty_x_TenYearSwap_ReturnsRate() 
    {
        //Arrange
        var startingDate = new Date(10,Month.October,2030); // starting date of 20x10yr swap
        var length= 10;
        repo.Setup(r => r.Read(It.IsAny<string>())).Returns(LoadSwapPoints()); // LoadSwapPoints returns IEnumerable<RateHelpers>

        //Act
        service.ConstructSwapPoints(SettlementDate);
        var instrumentRate = service.ImpliedRate(startingDate, length);

        //Assert
        Assert.That(instrumentRate, Is.Not.Null); // this must change to a value test

    }

This is part of the larger ConstructSwapPoints method

        var depoFRASwapInstruments = PointVector; // RateHelperVector populated with RateHelpers
        DayCounter termStructureDayCounter = new ActualActual(ActualActual.Convention.Actual365);

        QuoteHandleVector quotes = new QuoteHandleVector();
        DateVector quoteDates = new DateVector();

        py = CreatePiecewiseLinearCurve(settlementDate, depoFRASwapInstruments, termStructureDayCounter, quotes, quoteDates);
        DiscountingTermStructure = new RelinkableYieldTermStructureHandle(py); //RelinkableYieldTermStructureHandle
        //DiscountingTermStructure.linkTo(py); // alternate way

        PricingEngine = new DiscountingSwapEngine(DiscountingTermStructure); // DiscountingSwapEngine           

With the ImpliedRate method as follows (i have snipped some parts out due to IP restrictions);

    public double ImpliedRate(Date startingDate, int length)
    {

        var swapMaturityDate = startingDate.Add(new Period(length, TimeUnit.Years));
        var curveMaturityDate = py.maxDate();

        Schedule fixedSchedule = new Schedule(startingDate, swapMaturityDate, new Period(Frequency.Quarterly), SouthAfricanCalender, Convention, Convention, DateGeneration.Rule.Forward, false);
        Schedule floatSchedule = new Schedule(startingDate, swapMaturityDate, new Period(Frequency.Quarterly), SouthAfricanCalender, Convention, Convention, DateGeneration.Rule.Forward, false);

        VanillaSwap impliedSwap = new VanillaSwap(
            _VanillaSwap.Type.Payer, 
            10000000.0, 
            fixedSchedule, 
            0.1, 
            Actual365FixedDayCounter, 
            floatSchedule, 
            new Jibar(new Period(Frequency.Quarterly)), 
            0, 
            Actual365FixedDayCounter);

        impliedSwap.setPricingEngine(PricingEngine);

        return impliedSwap.fairRate(); // <---exception thrown here
    }

I hope my terminology is correct as the finance jargon is still new to me.

Edit: I have added the C++ tag, since I figure is actually related to some underlying C++ code. Hoping that this exposure may reveal some insights into what may be happening here.