Set ContinuationPoint (when browse is finished) to null instead of empty array, align with existing 1.5.xxx behavior

[koepalex]

This pull request standardizes the handling of the ContinuationPoint property in BrowseResult objects, ensuring it is always explicitly set to null (or its equivalent) when no continuation point is present. This change improves clarity and consistency in both the implementation and the tests, replacing checks for an "empty" continuation point with checks for a "null" continuation point.

Codebase consistency and correctness:

• All BrowseResult objects now explicitly set ContinuationPoint = default when no continuation point is to be returned, ensuring consistent initialization. (src/Opc.Ua.Server/NodeManager/MasterNodeManager.cs) [1] [2] [3]

Test updates for new semantics:

• All test assertions now use ContinuationPoint.IsNull instead of IsEmpty to check for the absence of a continuation point, reflecting the new contract. (tests/Opc.Ua.InformationModel.Tests/BrowseContinuationPointTests.cs, tests/Opc.Ua.Server.Tests/NodeManager/MasterNodeManagerDeterministicTests.cs) [1] [2] [3] [4] [5]

• Additional test cases have been added to verify that completed browse operations and error scenarios always return a null continuation point. (tests/Opc.Ua.Server.Tests/NodeManager/MasterNodeManagerDeterministicTests.cs) [1] [2] [3]# Description

Describe the changes here to communicate to the maintainers why they should accept this pull request. By default - this will become the Commit message after merging and thus define history.

Related Issues

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• Fixes #github-issue-number, ...

Checklist

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• I have signed the CLA and read the CONTRIBUTING doc.
• I have added tests that prove my fix is effective or that my feature works and increased code coverage.
• I have added all necessary documentation.
• I have verified that my changes do not introduce (new) build or analyzer warnings.
• I ran all tests locally using the UA.slnx solution against at least .net framework and .net 10, and all passed.
• I fixed all failing and flaky tests in the CI pipelines and all CodeQL warnings.
• I have addressed all PR feedback received.

[Copilot]

Pull request overview

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Standardizes BrowseResult.ContinuationPoint semantics so “no continuation point” is represented as null/default instead of an “empty” value, and aligns tests with the updated contract.

Changes:

• Initialize BrowseResult.ContinuationPoint to default in MasterNodeManager for both good and error results.
• Update test assertions to use ContinuationPoint.IsNull instead of IsEmpty.
• Add deterministic test coverage for null continuation points in completed/error browse flows.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 2 comments.

File	Description
src/Opc.Ua.Server/NodeManager/MasterNodeManager.cs	Explicitly sets ContinuationPoint = default when creating BrowseResult instances.
tests/Opc.Ua.Server.Tests/NodeManager/MasterNodeManagerDeterministicTests.cs	Adds/updates assertions and adds a new test validating null continuation points.
tests/Opc.Ua.InformationModel.Tests/BrowseTests.cs	Updates continuation point assertion to IsNull.
tests/Opc.Ua.InformationModel.Tests/BrowseContinuationPointTests.cs	Updates multiple assertions to IsNull for “no continuation point” cases.

[codecov]

Codecov Report

❌ Patch coverage is 66.66667% with 5 lines in your changes missing coverage. Please review.
✅ Project coverage is 73.56%. Comparing base (12f770b) to head (4ad5fbe).
⚠️ Report is 11 commits behind head on master.

Files with missing lines	Patch %	Lines
src/Opc.Ua.Server/NodeManager/MasterNodeManager.cs	66.66%	5 Missing ⚠️

❌ Your patch check has failed because the patch coverage (66.66%) is below the target coverage (80.00%). You can increase the patch coverage or adjust the target coverage.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #4057      +/-   ##
==========================================
- Coverage   73.86%   73.56%   -0.31%     
==========================================
  Files        1345     1345              
  Lines      180038   180093      +55     
  Branches    31678    31683       +5     
==========================================
- Hits       132993   132484     -509     
- Misses      36290    36900     +610     
+ Partials    10755    10709      -46     

Files with missing lines	Coverage Δ
src/Opc.Ua.Server/NodeManager/MasterNodeManager.cs	72.23% <66.66%> (-0.02%)	⬇️

... and 48 files with indirect coverage changes

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