[7.0.2 Cherry-pick] fix null ref in SqlDataReader

[github-actions]

Cherry-pick of #4159 (e0176e1) into release/7.0.

[cheenamalhotra]

/azp run

[azure-pipelines]

Azure Pipelines successfully started running 2 pipeline(s).

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 55.84%. Comparing base (f7b955c) to head (f08edb2).
⚠️ Report is 2 commits behind head on release/7.0.

❗ There is a different number of reports uploaded between BASE (f7b955c) and HEAD (f08edb2). Click for more details.

HEAD has 2 uploads less than BASE

Flag	BASE (f7b955c)	HEAD (f08edb2)
CI-SqlClient	2	0

Additional details and impacted files

@@               Coverage Diff                @@
##           release/7.0    #4206       +/-   ##
================================================
- Coverage        73.23%   55.84%   -17.40%     
================================================
  Files              280      275        -5     
  Lines            43025    65852    +22827     
================================================
+ Hits             31510    36772     +5262     
- Misses           11515    29080    +17565     

Flag	Coverage Δ
CI-SqlClient	?
PR-SqlClient-Project	55.84% <100.00%> (?)

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