Exception: unable to cast object of type ConstantTreeNode to NumberTreeNode in DerivativeCalculator

[gkronber]

To reproduce:

Create NLR and enter a model structure with a power (e.g. x ^ 2).

Run algorithm

Exception: HeuristicLab version: 3.3.16.8797 InvalidCastException: Unable to cast object of type 'HeuristicLab.Problems.DataAnalysis.Symbolic.ConstantTreeNode' to type 'HeuristicLab.Problems.DataAnalysis.Symbolic.NumberTreeNode'. at HeuristicLab.Problems.DataAnalysis.Symbolic.DerivativeCalculator.Derive(ISymbolicExpressionTreeNode branch, String variableName) in D:\reps\HeuristicLab\HeuristicLab.Problems.DataAnalysis.Symbolic\3.4\Converters\DerivativeCalculator.cs:line 159 at HeuristicLab.Problems.DataAnalysis.Symbolic.DerivativeCalculator.Derive(ISymbolicExpressionTreeNode branch, String variableName) in D:\reps\HeuristicLab\HeuristicLab.Problems.DataAnalysis.Symbolic\3.4\Converters\DerivativeCalculator.cs:line 68 at HeuristicLab.Problems.DataAnalysis.Symbolic.DerivativeCalculator.Derive(ISymbolicExpressionTreeNode branch, String variableName) in D:\reps\HeuristicLab\HeuristicLab.Problems.DataAnalysis.Symbolic\3.4\Converters\DerivativeCalculator.cs:line 139 at HeuristicLab.Problems.DataAnalysis.Symbolic.DerivativeCalculator.Derive(ISymbolicExpressionTreeNode branch, String variableName) in D:\reps\HeuristicLab\HeuristicLab.Problems.DataAnalysis.Symbolic\3.4\Converters\DerivativeCalculator.cs:line 98 at HeuristicLab.Problems.DataAnalysis.Symbolic.DerivativeCalculator.Derive(ISymbolicExpressionTreeNode branch, String variableName) in D:\reps\HeuristicLab\HeuristicLab.Problems.DataAnalysis.Symbolic\3.4\Converters\DerivativeCalculator.cs:line 119 at HeuristicLab.Problems.DataAnalysis.Symbolic.DerivativeCalculator.Derive(ISymbolicExpressionTreeNode branch, String variableName) in D:\reps\HeuristicLab\HeuristicLab.Problems.DataAnalysis.Symbolic\3.4\Converters\DerivativeCalculator.cs:line 68 at HeuristicLab.Problems.DataAnalysis.Symbolic.DerivativeCalculator.Derive(ISymbolicExpressionTreeNode branch, String variableName) in D:\reps\HeuristicLab\HeuristicLab.Problems.DataAnalysis.Symbolic\3.4\Converters\DerivativeCalculator.cs:line 85 at HeuristicLab.Problems.DataAnalysis.Symbolic.DerivativeCalculator.Derive(ISymbolicExpressionTreeNode branch, String variableName) in D:\reps\HeuristicLab\HeuristicLab.Problems.DataAnalysis.Symbolic\3.4\Converters\DerivativeCalculator.cs:line 68 at HeuristicLab.Problems.DataAnalysis.Symbolic.DerivativeCalculator.Derive(ISymbolicExpressionTree tree, String variableName) in D:\reps\HeuristicLab\HeuristicLab.Problems.DataAnalysis.Symbolic\3.4\Converters\DerivativeCalculator.cs:line 37 at HeuristicLab.Problems.DataAnalysis.Symbolic.Regression.SymbolicRegressionSolution.CalculateModelIntervals(ISymbolicRegressionSolution solution) in D:\reps\HeuristicLab\HeuristicLab.Problems.DataAnalysis.Symbolic.Regression\3.4\SymbolicRegressionSolution.cs:line 208 at HeuristicLab.Problems.DataAnalysis.Symbolic.Regression.SymbolicRegressionSolution.CalculateResults() in D:\reps\HeuristicLab\HeuristicLab.Problems.DataAnalysis.Symbolic.Regression\3.4\SymbolicRegressionSolution.cs:line 193 at HeuristicLab.Problems.DataAnalysis.Symbolic.Regression.SymbolicRegressionSolution..ctor(ISymbolicRegressionModel model, IRegressionProblemData problemData) in D:\reps\HeuristicLab\HeuristicLab.Problems.DataAnalysis.Symbolic.Regression\3.4\SymbolicRegressionSolution.cs:line 143 at HeuristicLab.Algorithms.DataAnalysis.NonlinearRegression.CreateRegressionSolution(IRegressionProblemData problemData, String modelStructure, Int32 maxIterations, Boolean applyLinearScaling, IRandom rand) in D:\reps\HeuristicLab\HeuristicLab.Algorithms.DataAnalysis\3.4\NonlinearRegression\NonlinearRegression.cs:line 289 at HeuristicLab.Algorithms.DataAnalysis.NonlinearRegression.Run(CancellationToken cancellationToken) in D:\reps\HeuristicLab\HeuristicLab.Algorithms.DataAnalysis\3.4\NonlinearRegression\NonlinearRegression.cs:line 197 at HeuristicLab.Optimization.BasicAlgorithm.Run(Object state) in D:\reps\HeuristicLab\HeuristicLab.Optimization\3.3\Algorithms\BasicAlgorithm.cs:line 130 at HeuristicLab.Optimization.BasicAlgorithm.Start(CancellationToken cancellationToken) in D:\reps\HeuristicLab\HeuristicLab.Optimization\3.3\Algorithms\BasicAlgorithm.cs:line 77