When the source mesh doesn't have the primary layers (CD_VERT for vdata, etc.) the returned mesh also didn't have those layers, even when non-zero elements were requested (for example requesting 4 vertices would still result in mvert = NULL).
When the source mesh doesn't have the primary layers (CD_VERT for vdata, etc.) the returned mesh also didn't have those layers, even when non-zero elements were requested (for example requesting 4 vertices would still result in mvert = NULL).