fix: allow empty only fix: actually allowed an empty value before a value was selected once, and not reset

[tthornton3-chwy]

Description

The allow empty option works if you had never selected a value in the array selector widget. As soon as you selected, and unselected, something though, it would never send ?state= again. Only a refresh would allow this to work again.

fixes: #10941

Motivation and Context

This change fixes an incoming issue where allow empty does not function properly after a value for the array is selected / unselected once.

I will create an issue and tag it momentarily.

How Has This Been Tested?

I have tested this locally, as well as included tests in the PR.

I used an api spec similar to this:

{
                        "name": "status",
                        "in": "query",
                        "description": "Find Something.",
                        "style": "form",
                        "explode": true,
                        "allowEmptyValue": true,
                        "schema": {
                            "anyOf": [
                                {
                                    "type": "array",
                                    "items": {
                                        "type": "string",
                                        "description": "Something.",
                                        "enum": [
                                            "FOO",
                                            "BAR"
                                        ]
                                    }
                                },
                                {
                                    "type": "null"
                                }
                                
                            ]
                        }
                    },

it functioned properly after my fix.

Screenshots (if appropriate):

Checklist

My PR contains...

• No code changes (src/ is unmodified: changes to documentation, CI, metadata, etc.)
• Dependency changes (any modification to dependencies in package.json)
• Bug fixes (non-breaking change which fixes an issue)
• Improvements (misc. changes to existing features)
• Features (non-breaking change which adds functionality)

My changes...

• are breaking changes to a public API (config options, System API, major UI change, etc).
• are breaking changes to a private API (Redux, component props, utility functions, etc.).
• are breaking changes to a developer API (npm script behavior changes, new dev system dependencies, etc).
• are not breaking changes.

Documentation

• My changes do not require a change to the project documentation.
• My changes require a change to the project documentation.
• If yes to above: I have updated the documentation accordingly.

Automated tests

• My changes can not or do not need to be tested.
• My changes can and should be tested by unit and/or integration tests.
• If yes to above: I have added tests to cover my changes.
• If yes to above: I have taken care to cover edge cases in my tests.
• All new and existing tests passed.