Make a cook book example for indexing into optional array

[ekiernan]

No description provided.

[kayleemathews]

Notes from Jess

Create a pseudo None value:

if (false) {
  String? none = "None"
}

Use the pseudo-none (from above) to pass an optional input from an optional array to a subworkflow:
input_name = if defined(input_names) then select_first([input_names])[idx] else none
Note that this is only needed because we are indexing into the optional array input. The optional input must be made non-optional in order to index into it. If indexing into an optional array is not necessary, the optional input can be passed directly to the subworkflow.

There also might be an example in the Cromwell repo