Fixed crash caused by non-freed reference

[david-puglielli]

Fix for #434.

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This change is 

[coveralls]

Coverage remained the same at 73.014% when pulling 10aa50c on david-puglielli:odbc32-crash-fix into 628e0c9 on Microsoft:dev.

[yukiwongky]

You're not going to include a test for this PR? Perhaps the one that begins a transaction and execute an invalid query. Iterate 20 times.

[Hadis-Knj]

should have test for both PDO and SQLSRV to confirm it is fixed in PDO and doesn't exist in SQLSRV

[david-puglielli]

Tests that crash because of the bug would still output the expected results/errors because the crash occurs after script execution has finished. Also, a test that crashes can still pass when run under run-tests.php, and there is no crash then. So a test that iterates beginTransaction() and query() 20 times could output whatever we want it to 20 times and then crash at the end, and run-tests.php won't catch it. We may need to use manual verification for this fix in future.

[codecov-io]

Codecov Report

Merging #589 into dev will increase coverage by 0.01%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##              dev     #589      +/-   ##
==========================================
+ Coverage   74.84%   74.86%   +0.01%     
==========================================
  Files          50       50              
  Lines       14933    14933              
==========================================
+ Hits        11177    11179       +2     
+ Misses       3756     3754       -2

Impacted Files	Coverage Δ
...x86/php-7.0.25-src/ext/pdo_sqlsrv/php_pdo_sqlsrv.h	65.38% <0%> (+3.84%)	⬆️
...x86/php-7.1.11-src/ext/pdo_sqlsrv/php_pdo_sqlsrv.h	100% <0%> (+5.88%)	⬆️

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[yukiwongky]

Should still include tests for "manual verification" in the future

[david-puglielli]

Tests for manual verification that are always skipped when testing automatically on Github? I'll upload tests for that.

[coveralls]

Coverage increased (+0.02%) to 73.037% when pulling 91418df on david-puglielli:odbc32-crash-fix into 628e0c9 on Microsoft:dev.

[coveralls]

Coverage increased (+0.02%) to 73.037% when pulling e79f46b on david-puglielli:odbc32-crash-fix into 628e0c9 on Microsoft:dev.

[coveralls]

Coverage increased (+0.02%) to 73.037% when pulling e2e82b2 on david-puglielli:odbc32-crash-fix into 628e0c9 on Microsoft:dev.

[coveralls]

Coverage increased (+0.02%) to 73.037% when pulling 4d627a0 on david-puglielli:odbc32-crash-fix into 628e0c9 on Microsoft:dev.