Error message when loading older version into Studio

[Nancy-Salpepi]

Test device
MacBook Air (m1 chip)

Operating System
macOS 12.4

Browser
Safari

Problem description
For phetsims/qa#818, when loading a saved state from the older version (1.4) into Studio version 1.5, an error appears in the console. I didn't see this error when testing Gravity and Orbits phetsims/qa#816.
After a quick check things seem to be working OK except for additional errors that appear in console when I press the Reset All button (I will post in separate issue).

Steps to reproduce

1. In Studio version 1.4, select the intro screen and press the Save button
2. Open Studio version 1.5.0-dev.1 and open the console.
3. Load the saved sim

Visuals

[pixelzoom]

This is (presumably) related to migration, a focus of this release. Assigning to @zepumph and @samreid.

[zepumph]

This is an expected new part of migration and credentials. We always try to request without credentials, and if we get back a 401 (credentials needed), then we request again with the credentials. Please update QA doc appropriately with this pattern. Feel free to close.

[Nancy-Salpepi]

OK. Got it. I will update QA book.