Selecting existing model from container during scene creation does not capture the blob URL

[msnyder-msft]

Describe the bug
When creating a new scene, if you select a 3D model for a file that is already in the container, the URL doesn't get stored on the scene and when you try to access the scene you get an uncaught exception.

To Reproduce
Steps to reproduce the behavior:

1. Go to Dev - https://dev.explorer.azuredigitaltwins-test.net/3DScenes/
2. Click on Create Scene
3. Fill in the details
4. Select a file from your container
5. Click create
6. Try to access that scene

Expected behavior

1. Should not let you save if it doesn't have a valid URL for a file.
2. Should store the URL for the existing file in the container when selecting a file

Screenshots