Re.g Pex error (object reference not set to an instance of an object)

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ASP.NET

When I am running pex in ASP.NET following error is producing. Can anyone help this to solve?

--- Description
failing test: NullReferenceException, Object reference not set to an instance of an object.

[TestMethod]
[PexGeneratedBy(typeof(ramosTest))]
[PexRaisedException(typeof(NullReferenceException))]
public void PopulateAllAirlines01()
{
    string s;
    s = this.PopulateAllAirlines((string)null, (string)null); //Error on this line
}

--- Exception details

System.NullReferenceException: Object reference not set to an instance of an object.    D:\Chenthil\Dev\FastidioV2\Fastidio\FastidioBizLayer\AirLineFacade.cs(102): at System.Collections.Generic.List`1<FastidioDTO.AirLineDto> FastidioBizFacade.AirLineFacade.FindAllAirLines() 
    D:\Chenthil\Dev\FastidioV2\Fastidio\FastidioUI\Masters\ramos.aspx.cs(749): at System.String FastidioUI.Masters.ramos.PopulateAllAirlines(System.String Param, System.String additions) 
      at System.String FastidioUI.Masters.ramosTest.PopulateAllAirlines(System.String Param, System.String additions) 
      at Microsoft.ExtendedReflection.Interpretation.Term Microsoft.ExtendedReflection.__DynamicMethods.invoke:FastidioUI.Masters.ramosTest.PopulateAllAirlines(Microsoft.ExtendedReflection.DataAccess.ITermConstructor`1<Microsoft.ExtendedReflection.Interpretation.Term> , Microsoft.ExtendedReflection.DataAccess.ITermDestructor`1<Microsoft.ExtendedReflection.Interpretation.Term> , Microsoft.ExtendedReflection.Interpretation.Term[] ) 
      at System.Void Microsoft.Pex.Engine.PathExecution.PathExecutorBase.InternalRun(Microsoft.ExtendedReflection.DataAccess.ITermDestructor`1<Microsoft.ExtendedReflection.Interpretation.Term> destructor, Microsoft.Pex.Engine.PathExecution.PathSegmentPreparer segmentPreparer, Microsoft.Pex.Engine.PathExecution.PathSegmentReporter segmentReporter, System.Collections.Generic.IEnumerable`1<Microsoft.Pex.Engine.PathExecution.PathSegment> segments) 
      at System.Boolean Microsoft.Pex.Engine.PathExecution.PathExecutorBase.TryRun(Microsoft.Pex.Engine.PathExecution.PexPathExecutionResult& runResult, Microsoft.ExtendedReflection.Interpretation.ISubstitution& finalSubstitution, Microsoft.ExtendedReflection.Interpretation.States.IState& finalState) 
      at System.Boolean Microsoft.Pex.Engine.Drivers.PexPathDriver.InternalRun(System.Object concreteFixtureObject) 
      at System.Boolean Microsoft.Pex.Engine.Drivers.PexPathDriver.Run(System.Object concreteFixtureObject) 
      at System.Void Microsoft.Pex.Engine.Drivers.PexExplorationDriver.InternalExplore() 
      at System.Void Microsoft.Pex.Engine.Drivers.PexExplorationDriver.CheckedExploreInternal() 
      at System.Void Microsoft.Pex.Engine.Drivers.PexExplorationDriver.Execute() 
      at System.Void Microsoft.Pex.Engine.Drivers.PexExplorationDriver.Explore() 
      at System.Void Microsoft.Pex.Engine.Drivers.PexDriver.ExecuteExploration(Microsoft.Pex.Engine.PexExplorationBase exploration) 
      at System.Void Microsoft.Pex.Engine.Drivers.PexDriver.ExecuteFixture(Microsoft.Pex.Engine.PexFixture fixture) 
      at System.Void Microsoft.Pex.Engine.Drivers.PexDriver.ExecuteAssembly() 
      at System.Void Microsoft.Pex.Engine.Drivers.PexDriver.ExecuteAll() 
      at System.Int32 Microsoft.Pex.Engine.Drivers.PexDriver.ExecuteExplorationProtected() 
      at System.Void Microsoft.Pex.Engine.Drivers.PexDriver.ExecuteExploration() 
      at System.Int32 Microsoft.Pex.Engine.PexEngineLauncher.ExecuteMonitored(Microsoft.ExtendedReflection.Utilities.AssemblyResolver resolver, Microsoft.Pex.Engine.PexEngineOptions options, System.Boolean inSandbox) 
      at System.Int32 Microsoft.Pex.Engine.PexEngineLauncher.Main(System.String[] args)