Fix unreported MSSQL bug with connections API

[elpaso]

Fix unreported MSSQL bug with connections API, the DB was destroyed and the next row was returning nothing.

[elpaso]

Spotted by running the tests locally, mssql test is not running on CI unfortunately.

[qgis-bot]

The backport to queued_ltr_backports failed:

The process '/usr/bin/git' failed with exit code 1

stderr

error: could not apply 0e3cd143fd... Fix unreported MSSQL bug with connections API
hint: After resolving the conflicts, mark them with
hint: "git add/rm <pathspec>", then run
hint: "git cherry-pick --continue".
hint: You can instead skip this commit with "git cherry-pick --skip".
hint: To abort and get back to the state before "git cherry-pick",
hint: run "git cherry-pick --abort".

stdout

Auto-merging src/providers/mssql/qgsmssqlproviderconnection.cpp
CONFLICT (content): Merge conflict in src/providers/mssql/qgsmssqlproviderconnection.cpp
Auto-merging src/providers/mssql/qgsmssqlproviderconnection.h

To backport manually, run these commands in your terminal:

# Fetch latest updates from GitHub
git fetch
# Create a new working tree
git worktree add .worktrees/backport-queued_ltr_backports queued_ltr_backports
# Navigate to the new working tree
cd .worktrees/backport-queued_ltr_backports
# Create a new branch
git switch --create backport-50194-to-queued_ltr_backports
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick 0e3cd143fd20214adf55b201737c7c4f2851a2cb
# Push it to GitHub
git push --set-upstream origin backport-50194-to-queued_ltr_backports
# Go back to the original working tree
cd ../..
# Delete the working tree
git worktree remove .worktrees/backport-queued_ltr_backports

Then, create a pull request where the base branch is queued_ltr_backports and the compare/head branch is backport-50194-to-queued_ltr_backports.