Error on swagger-ui: Cannot read property 'toString' of undefined

Q&A (please complete the following information)

• OS: macOS
• Browser: chrome
• Version: 89.0.4389.114
• Method of installation: npm
• Swagger-UI version: 3.46.0
• Swagger/OpenAPI version: OpenAPI 3.0

Content & configuration

Example Swagger/OpenAPI definition:

openapi: 3.0.1
info:
  title: OpenAPI definition
  version: v0
servers:
  - url: 'http://localhost:8080'
    description: Generated server url
paths:
  /hello:
    get:
      tags:
        - hello
      operationId: hello
      parameters:
        - name: user
          in: query
          required: true
          schema:
            $ref: '#/components/schemas/User'
        - name: someEnums
          in: query
          description: SomeEum decs
          content:
            '*/*':
              schema:
                type: array
                items:
                  type: string
                  enum:
                    - FIRST
                    - SECOND
        - name: textSet
          in: query
          description: First decs
          content:
            '*/*':
              schema:
                type: array
                items:
                  type: string
        - name: someText
          in: query
          description: Second decs
          content:
            '*/*':
              schema:
                type: string
      responses:
        '200':
          description: OK
          content:
            '*/*':
              schema:
                type: string
components:
  schemas:
    User:
      type: object
      properties:
        someText:
          type: string
        textSet:
          uniqueItems: true
          type: array
          items:
            type: string
        someEnums:
          uniqueItems: true
          type: array
          items:
            type: string
            enum:
              - FIRST
              - SECOND

Swagger-UI configuration options: Default swagger-ui configuration

url=http://localhost:8080/v3/api-docs

Describe the bug you're encountering

Swagger UI fails to execute request when one of query parameters is not filled out using the yaml sample.
It works only when you fill out all the query parameters (then you can remove any of the filled out parameters and no error would occur).

To reproduce...

Steps to reproduce the behavior:

1. Go to the swagger-ui'
2. Click on 'Try it'
3. Click on 'Execute'
4. See error on the browser console:

TypeError: Cannot read property 'toString' of undefined
    at Xn (content-serializer.js:18)
    at er (parameter-builders.js:43)
    at index.js:241
    at Array.forEach (<anonymous>)
    at Object.dr [as buildRequest] (index.js:196)
    at actions.js:452
    at utils.js:177
    at bindActionCreators.js:3
    at wrap-actions.js:33
    at Object.r (system.js:174)
(anonymous) @ system.js:464

Expected behavior

Requests executed as expected.

Screenshots

Additional context or thoughts

As a workaround, when the OpenAPI definition doesn't contain content: element, but only schema: referenced directly, it works.

Reproduce the failure with the provided OpenAPI 3.0 YAML and Swagger UI configuration, leaving one query parameter empty. Start at content-serializer.js:18 and parameter-builders.js:43, then trace the buildRequest entry point in index.js. Done means the sample request executes successfully with an unfilled query parameter, without the toString error.