vtkPVDiscretizableColorTransferFunction: Index out of range !

Warnings are raised everytime you move your mouse over the Opacity transfer function in a certain case.

Reproduce:

• enable volume rendering on something (just to have the mapping data show up)
• In mapping data: add more points (nodes) in the opacity transfer function than in the Color transfer functions
• hover your mouse over the Opacity transfer function graph: you get

(1712.476s) [paraview        ]vtkColorTransferFunctio:1277   ERR| vtkPVDiscretizableColorTransferFunction (0x55e84103da50): Index out of range!

Brief analysis

Warning is raised here: https://gitlab.kitware.com/vtk/vtk/-/blob/4b9e1acc53af9ccf54df4b0c78909ff172319a71/Rendering/Core/vtkColorTransferFunction.cxx#L1274

The issue here is that the this->Internal->Nodes.size() there always returns the number of nodes in the color transfer function (try it out yourself with a print), even when used in the opacity transfer functions. I tried for quite some time to figure out why but eventually couldn't so I'm raising this issue.

Have a great day