Bugzilla

### Beta/Release Uplift Approval Request
* **User impact if declined**: Patch is going to help conduct nimbus holdback study and closely simulate 88 default onboarding experience in 89
* **Is this code covered by automated tests?**: Yes
* **Has the fix been verified in Nightly?**: Yes
* **Needs manual test from QE?**: Yes
* **If yes, steps to reproduce**: - Launch local build ./mach run --temp-profile about:welcome , set pref nimbus.debug to true. 
- Open about:studies?optin_slug=identity-based-new-user-onboarding-v2&optin_branch=msw_treatment_88&optin_collection=nimbus-preview
should enroll user in treatment branch of identity-based-new-user-onboarding-v2 experiment on stage RS

- open about:welcome should show Fx 88 experience
- Set browser.newtabpage.activity-stream.asrouter.devtoolsEnabled as true, Open about:newtab#devtools -> Targeting and Force addon attribution , Open about:welcome , should see RTAMO page
* **List of other uplifts needed**: none
* **Risk to taking this patch**: Low
* **Why is the change risky/not risky? (and alternatives if risky)**: Small patch needed for nimbus experiment when screens content is not defined for experiments. Default flow always has screen content and well tested for onboarding
* **String changes made/needed**: None

### Beta/Release Uplift Approval Request
* **User impact if declined**: Patch is going to help conduct nimbus holdback study and closely simulate 88 default onboarding experience in 89
* **Is this code covered by automated tests?**: Yes
* **Has the fix been verified in Nightly?**: Yes
* **Needs manual test from QE?**: Yes
* **If yes, steps to reproduce**: See Test plan in https://phabricator.services.mozilla.com/D115549
* **List of other uplifts needed**: none
* **Risk to taking this patch**: Low
* **Why is the change risky/not risky? (and alternatives if risky)**: Small patch needed for nimbus experiment when screens content is not defined for experiments. Default flow always has screen content and well tested for onboarding
* **String changes made/needed**: None