#4033 [BUG] Optional list arg is causing UI launch form to white screen Issue created by lauralindy Describe the bug After upgrading to 1.9.0 or 1.9.1, when I click on the launch form or relaunch form for workflows that have optional list args, the page will just flash the form and then go white screen. Non-optional lists don't do this. Expected behavior Form should open up and allow input. Additional context to reproduce

from flytekit import task, workflow
import typing

@task
def some_task(a: typing.Optional[typing.List[int]]):
    print(a)

@workflow
def my_wf(x: typing.Optional[typing.List[int]]):
    some_task(a=x)

Screenshots console logs

react-dom.production.min.js:125 Error: empty string
    at Function.d [as fromString] (vendor.d3268180b8c0d189c23e.js:2:21291)
    at Object.toLiteral (main.7d9178e441dc822c8094.js:1:299325)
    at Object.typeDefinitionToDefaultValue (main.7d9178e441dc822c8094.js:1:294199)
    at main.7d9178e441dc822c8094.js:1:266673
    at Array.reduce (<anonymous>)
    at main.7d9178e441dc822c8094.js:1:266522
    at t.UnionInput (main.7d9178e441dc822c8094.js:1:266721)
    at we (react-dom.production.min.js:84:293)
    at zj (react-dom.production.min.js:226:496)
    at Th (react-dom.production.min.js:152:223)
Me @ react-dom.production.min.js:125
main.7d9178e441dc822c8094.js:1 Error: empty string
    at Function.d [as fromString] (vendor.d3268180b8c0d189c23e.js:2:21291)
    at Object.toLiteral (main.7d9178e441dc822c8094.js:1:299325)
    at Object.typeDefinitionToDefaultValue (main.7d9178e441dc822c8094.js:1:294199)
    at main.7d9178e441dc822c8094.js:1:266673
    at Array.reduce (<anonymous>)
    at main.7d9178e441dc822c8094.js:1:266522
    at t.UnionInput (main.7d9178e441dc822c8094.js:1:266721)
    at we (react-dom.production.min.js:84:293)
    at zj (react-dom.production.min.js:226:496)
    at Th (react-dom.production.min.js:152:223)

Are you sure this issue hasn't been raised already? ☑︎ Yes Have you read the Code of Conduct? ☑︎ Yes flyteorg/flyte