Editing a template which contains UxmlObjects throws null reference exceptions and breaks the inspector.

Steps to reproduce:

1. Open the test project "Modules\UIBuilder\Tests\EditModeAndPlayModeTests\UIBuilder"
2. Open UxmlSerializedDataUxmlAttributesViewTestDocument.uxml in the UI Builder
3. In the Library view search for and add UXMLObjectDocument
4. Select multi-column-list-view from the TemplateContainer
5. The inspector will break and errors will spam the console.

Actual results: Can see the inspector for the element without errors

Expected results: No inspector and errors.

Reproducible with versions: 6000.0.11f1

Not reproducible with versions: NA

Can’t test with versions: 

Tested on (OS): Windows

Notes:

• We are likely trying to extract the UxmlObjects from the wrong asset