vtkMatplotlibMathTextUtilities: Fix crash in StringToPath
One of the GetPointer()
calls removed by !3337 (merged) was necessary because it is passed to a variadic function
where no automatic coersion to a pointer occurs.
EDIT: When first opened this MR also converted some NULL
to nullptr
to fix comparisons. That is handled by !3384 (merged) instead.
Edited by Brad King