The error is that the value for the second element is missing:
venture[script] > dict(["a", 1], ["b"])
*** evaluation: Index out of bounds: VentureNumber(1.0)
(autorun (dict (array "a" 1) (array "b")))
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Caused by
Index out of bounds: VentureNumber(1.0)
The error is that the value for the second element is missing: