Error: (string-length) bad argument type: ("" "" "...

        Call history:

        <syntax>          (##core#ensure-toplevel-definition get-input-data)
        <syntax>          (##core#undefined)
        <syntax>          (##core#set! get-input-data (##core#lambda () (call-with-input-file config-filename (lambda (p) (rea...
        <syntax>          (##core#lambda () (call-with-input-file config-filename (lambda (p) (read-lines p))))
        <syntax>          [get-input-data] (##core#begin (call-with-input-file config-filename (lambda (p) (read-lines p))))
        <syntax>          [get-input-data] (call-with-input-file config-filename (lambda (p) (read-lines p)))
        <syntax>          [get-input-data] (lambda (p) (read-lines p))
        <syntax>          [get-input-data] (##core#lambda (p) (read-lines p))
        <syntax>          [get-input-data] (##core#begin (read-lines p))
        <syntax>          [get-input-data] (read-lines p)
        <syntax>          (yaml-load (get-input-data))
        <syntax>          (get-input-data)
        <eval>    (yaml-load (get-input-data))
        <eval>    (get-input-data)
        <eval>    [get-input-data] (call-with-input-file config-filename (lambda (p) (read-lines p)))
        <eval>    [get-input-data] (read-lines p)       <--