fix bg stats invalid access

[sfc-gh-jslocum]

Fixes incorrect logic on when to add snapshot rows stats

Code-Reviewer Section

The general pull request guidelines can be found here.

Please check each of the following things and check all boxes before accepting a PR.

• The PR has a description, explaining both the problem and the solution.
• The description mentions which forms of testing were done and the testing seems reasonable.
• Every function/class/actor that was touched is reasonably well documented.

For Release-Branches

If this PR is made against a release-branch, please also check the following:

• This change/bugfix is a cherry-pick from the next younger branch (younger release-branch or main if this is the youngest branch)
• There is a good reason why this PR needs to go into a release branch and this reason is documented (either in the description above or in a linked GitHub issue)

[foundationdb-ci]

Result of foundationdb-pr-clang-ide on Linux CentOS 7

• Commit ID: f1d68fb
• Duration 0:16:27
• Result: ✅ SUCCEEDED
• Error: N/A
• Build Logs (available for 30 days)
• Build Artifact (available for 30 days)

[fdb-windows-ci]

Doxense CI Report for Windows 10

• Commit ID: f1d68fb
• Result: ✔️ SUCCEEDED
• Build Logs (available for 30 days)

[foundationdb-ci]

Result of foundationdb-pr-macos-m1 on macOS BigSur 11.5.2

• Commit ID: f1d68fb
• Duration 0:38:48
• Result: ✅ SUCCEEDED
• Error: N/A
• Build Logs (available for 30 days)
• Build Artifact (available for 30 days)

[foundationdb-ci]

Result of foundationdb-pr-macos on macOS Monterey 12.x

• Commit ID: f1d68fb
• Duration 0:42:22
• Result: ✅ SUCCEEDED
• Error: N/A
• Build Logs (available for 30 days)
• Build Artifact (available for 30 days)

[foundationdb-ci]

Result of foundationdb-pr-clang on Linux CentOS 7

• Commit ID: f1d68fb
• Duration 0:50:00
• Result: ❌ FAILED
• Error: Error while executing command: if python3 -m joshua.joshua list --stopped | grep ${ENSEMBLE_ID} | grep -q 'pass=10[0-9][0-9][0-9]'; then echo PASS; else echo FAIL && exit 1; fi. Reason: exit status 1
• Build Logs (available for 30 days)
• Build Artifact (available for 30 days)

[foundationdb-ci]

Result of foundationdb-pr on Linux CentOS 7

• Commit ID: f1d68fb
• Duration 0:59:55
• Result: ✅ SUCCEEDED
• Error: N/A
• Build Logs (available for 30 days)
• Build Artifact (available for 30 days)

[foundationdb-ci]

Result of foundationdb-pr-cluster-tests on Linux CentOS 7

• Commit ID: f1d68fb
• Duration 1:27:18
• Result: ❌ FAILED
• Error: Error while executing command: if $(grep -q -- "--- FAIL:" ${CODEBUILD_SRC_DIR}/fdb-kubernetes-tests/logs/*.log); then echo "TESTS FAILED SEE THESE LOGS:"; echo ; grep -l -- "--- FAIL:" ${CODEBUILD_SRC_DIR}/fdb-kubernetes-tests/logs/*.log; exit 1; fi. Reason: exit status 1
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[sfc-gh-anoyes]

@jzhou77 the failure is unrelated to this change, and this change addresses a memory error coming up in the asan nightly. Can you merge this please?

[foundationdb-ci]

Result of foundationdb-pr-clang-ide on Linux CentOS 7

• Commit ID: b46c9dc
• Duration 0:18:23
• Result: ✅ SUCCEEDED
• Error: N/A
• Build Logs (available for 30 days)
• Build Artifact (available for 30 days)

[fdb-windows-ci]

Doxense CI Report for Windows 10

• Commit ID: b46c9dc
• Result: ✔️ SUCCEEDED
• Build Logs (available for 30 days)

[foundationdb-ci]

Result of foundationdb-pr on Linux CentOS 7

• Commit ID: b46c9dc
• Duration 0:58:26
• Result: ✅ SUCCEEDED
• Error: N/A
• Build Logs (available for 30 days)
• Build Artifact (available for 30 days)

[foundationdb-ci]

Result of foundationdb-pr-clang on Linux CentOS 7

• Commit ID: b46c9dc
• Duration 1:00:46
• Result: ✅ SUCCEEDED
• Error: N/A
• Build Logs (available for 30 days)
• Build Artifact (available for 30 days)

[foundationdb-ci]

Result of foundationdb-pr-cluster-tests on Linux CentOS 7

• Commit ID: b46c9dc
• Duration 1:15:14
• Result: ✅ SUCCEEDED
• Error: N/A
• Build Logs (available for 30 days)
• Build Artifact (available for 30 days)