[Cherry-pick] DYN-10493: Fix crash in Getting Started guided tour

[github-actions]

Cherry-pick of #17111 to RC4.1.1_master

Purpose

Fixes DYN-10493: Dynamo crashes when clicking "Start Tour" on the Getting Started guided tour (Learning tab). The crash occurs on the transition from the Welcome popup to step 2 ("nodes").

Root cause: GuidesValidationMethods.HighlightPort calls ItemContainerGenerator.ContainerFromItem to locate the WPF container for a port, then passes the result to CreateRectangle. ContainerFromItem can return null when the ItemsControl hasn't generated containers yet. This is a timing race exposed by PR #16883 (DYN-7760, Feb 17 2026), which added synchronous WebView2 extension-closing before tour startup — shifting the dispatcher queue state enough to delay container generation past the point where HighlightPort reads it. The resulting null reached NameScope.SetNameScope inside CreateRectangle, which throws ArgumentNullException("dependencyObject").

Key changes:

• Added a null guard on mainGrid in HighlightPort (GuidesValidationMethods.cs) — skips the port highlight rather than crashing if the container isn't ready. The tour continues without the visual effect.

Regression introduced in: PR #16883 (DYN-7760, Feb 17 2026)
Not reproducible in: 4.0.2 and older
Fix targets: master, cherry-pick to 4.1.1

Full investigation: DYN-10493 DynaNote (Autodesk internal)

Declarations

• Is documented according to the standards
• The level of testing this PR includes is appropriate
• Changes to the API follow Semantic Versioning and are documented in the API Changes document.

Release Notes

Fixed a crash that occurred when clicking "Start Tour" on the Getting Started guided tour (Learning tab).

Reviewers

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FYIs

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[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[jasonstratton]

Successfully Rerun:
SonarQube Scan - https://c007.cloudbees-ci.autodesk.com/job/DYNCI/job/Dynamo/job/DynamoCACoverage/job/SonarPrScan/183/
SelfServe - https://c007.cloudbees-ci.autodesk.com/job/DYNCI/job/Dynamo/job/DynamoSelfServe/job/pullRequestValidation/222/

Looks like Smoke Tests never run - Rerunning now: https://c007.cloudbees-ci.autodesk.com/job/DYNCI/job/Dynamo/job/DynamoAGTTests/job/smoke/204/

[jasonstratton]

Smoke Test failed 3 times in a row
https://c007.cloudbees-ci.autodesk.com/job/DYNCI/job/Dynamo/job/DynamoAGTTests/job/smoke/204/
https://c007.cloudbees-ci.autodesk.com/job/DYNCI/job/Dynamo/job/DynamoAGTTests/job/smoke/205/
https://c007.cloudbees-ci.autodesk.com/job/DYNCI/job/Dynamo/job/DynamoAGTTests/job/smoke/206/

20:52:29 C:\Jenkins\workspace\YNCI_Dynamo_DynamoAGTTests_smoke\repositories\Dynamo\src\Libraries\DynamoUnits\UnitsCore.csproj(46,5): error MSB3030: Could not copy the file "C:\Users\CDABuildGuy.nuget\packages\forgeunits.net\5.3.2\lib\net6.0\ForgeUnitsManaged.dll" because it was not found.

Odd that this just started, but it would seem unrelated to this cherry picked code change

Merging and will inform QA of the Smoke Test failures