v3dv/pipeline: null check for pCreateInfo->pDepthStencilState

This prevents a crash when the validation layers are enabled for some
of our ubo tests. Again, it seems that if some attachments are
missing, the validation layers remove some of the structs from the
pCreateInfo.

Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/6766>
1 file changed