Values do not stick when Boutiques input list parameter is optional

[MontrealSergiy]

If an input parameter explicitly declared optional in the boutiques, the cbrain would drop any values that user may assign to this parameter, at the least for lists.

Create a simple boutiques that includes an optional input, for example

{ "command-line-flag": "-l2", "value-key": "[L2]", "optional": true, "list": true, "type": "Number", "id": "l2", "name": "list", "description": "several numeric values" }

It is essential that optional attribute is set to true value. Deploy the boutiques, create task where the list l2 value is non-empty. While you would expect the values to keep they disappear after submissions. It is also apparent on parameter preview.

Notes. Did not check non-list parameters.

[prioux]

I am pretty sure this will be fixed as part of my PR #1145 ; it's one of the bugs I discovered while working on the main issue

[natacha-beck]

It is still buggy when we have a list.