fix: Fix problematic error returns

[cuishuang]

If err is not assigned a value here, the default err (must be nil) is returned.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 0% with 1 line in your changes missing coverage. Please review.

Project coverage is 74.80%. Comparing base (d27f997) to head (c7945ad).

Files with missing lines	Patch %	Lines
mssql_go19.go	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #241      +/-   ##
==========================================
- Coverage   74.91%   74.80%   -0.11%     
==========================================
  Files          32       32              
  Lines        6457     6458       +1     
==========================================
- Hits         4837     4831       -6     
- Misses       1332     1337       +5     
- Partials      288      290       +2     

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