Fix SqlCommand.Cancell null ref exception

[mdaigle]

No description provided.

[Copilot]

Pull request overview

This pull request fixes a NullReferenceException in SqlCommand.Cancel() when the command has no associated connection (Connection == null), aligning the method with expected no-op behavior in that scenario.

Changes:

• Prevent SqlCommand.Cancel() tracing from dereferencing _activeConnection when it is null.
• Add a functional test asserting Cancel() does not throw when Connection is null.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
src/Microsoft.Data.SqlClient/src/Microsoft/Data/SqlClient/SqlCommand.cs	Makes Cancel() correlation tracing null-safe for ClientConnectionId when _activeConnection is not set.
src/Microsoft.Data.SqlClient/tests/FunctionalTests/SqlCommandTest.cs	Adds regression coverage ensuring SqlCommand.Cancel() is a no-op when Connection is null.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 63.45%. Comparing base (47f4e52) to head (b5d889c).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4372      +/-   ##
==========================================
- Coverage   65.39%   63.45%   -1.95%     
==========================================
  Files         285      280       -5     
  Lines       43331    66193   +22862     
==========================================
+ Hits        28337    42000   +13663     
- Misses      14994    24193    +9199     

Flag	Coverage Δ
CI-SqlClient	?
PR-SqlClient-Project	63.45% <100.00%> (?)

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