bug: expanding model when query param showExtensions=true exists

[tim-lai]

Description

In the ObjectModel, insert a table cell td into the table row tr. Then insert empty space   into the table cell.

Motivation and Context

1. load SwaggerUI in dev mode
2. use 2 query parameters, e.g. http://localhost:3200/?docExpansion=full&showExtensions=true
3. expand any model
4. console error

warning.js:33 Warning: validateDOMNesting(...): Whitespace text nodes cannot appear as a child of <tr>.

How Has This Been Tested?

Following the above steps no longer produces the error with this 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.

[tim-lai]

please build

[shockey]

LGTM aside from the unrelated changes included in model.jsx — please resolve before merging this!

[shockey]

likewise, looks like #5914 snuck in here!