Swagger UI doesn't know how to deal when URLS is empty array

Q&A (please complete the following information)

• OS: linux (Ubuntu 18.04)
• Browser: google Chrome
• Version: 78.0.3904.50
• Method of installation: webjars Clasic
• Swagger-UI version: 3.23.8
• Swagger/OpenAPI version: OpenAPI 3.0

Content & configuration

Swagger-UI configuration options:

SwaggerUI({
 urls: [ ]
})

Describe the bug you're encountering

Swagger UI doesn't know hot to render when URLS parameter is an empty array ("[]"). It reports an error

To reproduce...

Steps to reproduce the behavior:

1. open swaggerUI
2. extend address with "?urls=[]" OR change inital swaggerUI configuration inside index.html to something like:

SwaggerUI({
 urls: [ ]
})

Expected behavior

I expect that topbar will be with empty selector.