unroll-column throws an exception when dataset has one column

[genmeblog]

(def data (tech.v3.dataset/->dataset {:a [[1 2 3] [4 5] [6 7 8]]}))

data
;; => _unnamed [3 1]:
;;    |      :a |
;;    |---------|
;;    | [1 2 3] |
;;    |   [4 5] |
;;    | [6 7 8] |

(tech.v3.dataset/unroll-column data :a)
;; exception

(def data2 (tech.v3.dataset/add-or-update-column data :b [-1 -2 -3]))

data2
;; => _unnamed [3 2]:
;;    |      :a | :b |
;;    |---------|---:|
;;    | [1 2 3] | -1 |
;;    |   [4 5] | -2 |
;;    | [6 7 8] | -3 |

(tech.v3.dataset/unroll-column data2 :a)
;; => _unnamed [8 2]:
;;    | :b | :a |
;;    |---:|---:|
;;    | -1 |  1 |
;;    | -1 |  2 |
;;    | -1 |  3 |
;;    | -2 |  4 |
;;    | -2 |  5 |
;;    | -3 |  6 |
;;    | -3 |  7 |
;;    | -3 |  8 |

Exception is:

1. Unhandled java.lang.IllegalArgumentException
   No implementation of method: :select of protocol:
   #'tech.v3.protocols.column/PColumn found for class: nil

          core_deftype.clj:  583  clojure.core/-cache-protocol-fn
          core_deftype.clj:  575  clojure.core/-cache-protocol-fn
                column.clj:   12  tech.v3.protocols.column/eval19236/fn/G
                column.clj:  117  tech.v3.dataset.column/select
                column.clj:  110  tech.v3.dataset.column/select
                  base.clj:  385  tech.v3.dataset.base/select-rows
                  base.clj:  380  tech.v3.dataset.base/select-rows
           dataset_api.clj: 1082  tech.v3.dataset-api/unroll-column
           dataset_api.clj:  996  tech.v3.dataset-api/unroll-column
           dataset_api.clj: 1025  tech.v3.dataset-api/unroll-column
           dataset_api.clj:  996  tech.v3.dataset-api/unroll-column
               dataset.clj: 1301  tech.v3.dataset/unroll-column
               dataset.clj: 1272  tech.v3.dataset/unroll-column
                      REPL:  110  tablecloth.playground/eval34794