Reset of cross-validation throws exception

[gkronber]

1. create new cross-validation
2. add executable algorithm (for instance symbolic regression demo) via drag and drop
3. click on reset button
4. => unhandled exception

in r4725

System.NullReferenceException was unhandled
Message: Object reference not set to an instance of an object.


NullReferenceException: Object reference not set to an instance of an object.
   at HeuristicLab.Algorithms.DataAnalysis.CrossValidation.Prepare()
   at HeuristicLab.Algorithms.DataAnalysis.CrossValidation.Prepare(Boolean clearRuns)
   at HeuristicLab.Algorithms.DataAnalysis.Views.CrossValidationView.resetButton_Click(Object sender, EventArgs e)
   at System.Windows.Forms.Control.OnClick(EventArgs e)
   at System.Windows.Forms.Button.OnClick(EventArgs e)
   at System.Windows.Forms.Button.OnMouseUp(MouseEventArgs mevent)
   at System.Windows.Forms.Control.WmMouseUp(Message& m, MouseButtons button, Int32 clicks)
   at System.Windows.Forms.Control.WndProc(Message& m)
   at System.Windows.Forms.ButtonBase.WndProc(Message& m)
   at System.Windows.Forms.Button.WndProc(Message& m)
   at System.Windows.Forms.Control.ControlNativeWindow.OnMessage(Message& m)
   at System.Windows.Forms.Control.ControlNativeWindow.WndProc(Message& m)
   at System.Windows.Forms.NativeWindow.DebuggableCallback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)
   at System.Windows.Forms.UnsafeNativeMethods.DispatchMessageW(MSG& msg)
   at System.Windows.Forms.Application.ComponentManager.System.Windows.Forms.UnsafeNativeMethods.IMsoComponentManager.FPushMessageLoop(Int32 dwComponentID, Int32 reason, Int32 pvLoopData)
   at System.Windows.Forms.Application.ThreadContext.RunMessageLoopInner(Int32 reason, ApplicationContext context)
   at System.Windows.Forms.Application.ThreadContext.RunMessageLoop(Int32 reason, ApplicationContext context)
   at System.Windows.Forms.Application.Run(Form mainForm)
   at HeuristicLab.Optimizer.HeuristicLabOptimizerApplication.Run()
   at HeuristicLab.PluginInfrastructure.DefaultApplicationManager.Run(ApplicationDescription appInfo) in c:\01 TeamCity\buildAgent\work\e9dc8b58e474af3e\HeuristicLab.PluginInfrastructure\3.3\DefaultApplicationManager.cs:line 123
   at HeuristicLab.PluginInfrastructure.DefaultApplicationManager.Run(ApplicationDescription appInfo)
   at HeuristicLab.PluginInfrastructure.Manager.PluginManager.Run(ApplicationDescription appInfo) in c:\01 TeamCity\buildAgent\work\e9dc8b58e474af3e\HeuristicLab.PluginInfrastructure\3.3\Manager\PluginManager.cs:line 131
   at HeuristicLab.PluginInfrastructure.Starter.StarterForm.<>c__DisplayClass8.<StartApplication>b__6() in c:\01 TeamCity\buildAgent\work\e9dc8b58e474af3e\HeuristicLab.PluginInfrastructure\3.3\Starter\StarterForm.cs:line 145

[mkommend]

Corrected cloning of CrossValidation with r4735.

[gkronber]

Tested with GP symbolic regression demo.