The TestFunctions evaluators throw an exception after changing the problem

[jkarder]

Create a new PSO algorithm, add a new TestFunctions problem, change the problem and run the algorithm.

OperatorExecutionException: An exception was thrown by the operator "AckleyEvaluator": Object reference not set to an instance of an object.
   at HeuristicLab.SequentialEngine.SequentialEngine.Run(CancellationToken cancellationToken)
   at HeuristicLab.Core.Engine.Run(Object state)
   at System.Threading.Tasks.Task.Execute()
-----
NullReferenceException: Object reference not set to an instance of an object.
   at HeuristicLab.Problems.TestFunctions.AckleyEvaluator.Apply(RealVector point)
   at HeuristicLab.Problems.TestFunctions.AckleyEvaluator.EvaluateFunction(RealVector point)
   at HeuristicLab.Problems.TestFunctions.SingleObjectiveTestFunctionProblemEvaluator.Apply()
   at HeuristicLab.Operators.Operator.Execute(IExecutionContext context, CancellationToken cancellationToken)
   at HeuristicLab.SequentialEngine.SequentialEngine.Run(CancellationToken cancellationToken)

[epitzer]

r7781 allow preparing PSO with invalid problem and configure algorithm to run until the PSO main loop which does nothing (similar to e.g. Tabu Search)

[abeham]

ok