fixes assert in !2950.
requested to merge utkarsh.ayachit/paraview:17821-spreadsheet-and-multiblock-inspector-fixes into master
fixes pv.OpenSaveData test failure due to the flags not getting reset correctly after reset session. that was because we were using QPointer to check if the representationw as changed, which is not adequate since QPointer can be nulled externally. fixed by using a void-ptr to catch change in representation pointer.
Closes #17821 (closed)