ORDER BY clause referencing named column crashes

[cswinter]

SELECT pickup_ntaname, count(0) AS c FROM default ORDER BY c;

ERROR 2023-09-17T20:02:29Z: locustdb::engine::planning::query_plan: encoding_range not implement for NullVec { len: 10000, nulls: TypedBufferRef { buffer: BufferRef { i: 2, name: "nulls", t: PhantomData<locustdb::engine::execution::buffer::Any> }, tag: Null } }

This query works:

SELECT pickup_ntaname, count(0) AS c FROM default ORDER BY pickup_ntaname;