[6.0] Cherry-pick of #3270 - Handle null socket

[paulmedynski]

Cherry-pick of #3270.

[codecov]

Codecov Report

Attention: Patch coverage is 60.00000% with 2 lines in your changes missing coverage. Please review.

Project coverage is 72.73%. Comparing base (cfb007d) to head (431a4bf).
Report is 8 commits behind head on release/6.0.

Files with missing lines	Patch %	Lines
...e/src/Microsoft/Data/SqlClient/SNI/SNITcpHandle.cs	60.00%	2 Missing ⚠️

Additional details and impacted files

@@               Coverage Diff               @@
##           release/6.0    #3283      +/-   ##
===============================================
- Coverage        72.78%   72.73%   -0.06%     
===============================================
  Files              285      285              
  Lines            59162    59165       +3     
===============================================
- Hits             43064    43036      -28     
- Misses           16098    16129      +31     

Flag	Coverage Δ
addons	92.58% <ø> (ø)
netcore	75.60% <60.00%> (+0.05%)	⬆️
netfx	71.03% <ø> (-0.13%)	⬇️

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