Potential vtkUnstructuredGrid::ShallowCopy from vtkUnstructuredGridBase crash

We’re using a vtkMappedUnstructuredGrid for our input data. One of our filters takes our type as input, adds data and is supposed to output a regular vtkUnstructuredGrid. We ran into a crash situation with this scenario because of the following:

At some point during pipeline execution the executive calls vtkUnstructuredGrid::Initialize when it prepares the filter output. This deletes the connectivity and types arrays. However, filters may then call vtkUnstructuredGrid::ShallowCopy in RequestData. This is a problem because there is special handling for vtkUnstructuredGridBase and the connectivity and type arrays are not recreated before a call to vtkUnstructuredGrid::InternalInsertNextCell, resulting in a crash.

For example this will crash:

// vtkUnstructuredGridBase subclass other than vtkUnstructuredGrid, e.g. vtkMappedUnstructuredGrid
vtkSmartPointer<vtkMyMappedGrid> source = ...; 
vtkNew<vtkUnstructuredGrid> ug;
ug->ShallowCopy(source); // crashes

Are we using it wrong? Or am I correct that vtkUnstructuredGrid::ShallowCopy requires a check an potential allocation there?

Happy to prepare a fix if this turns out to be a bug.