Fix bug with GetShardsCount() == 0

[dahbka-lis]

Changelog entry

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Changelog category

• Not for changelog (changelog entry is not required)

Description for reviewers

Fix bug when BufferWriteActor is committing changes, getting 0 shards and starting distributed commit -> doing nothing.

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[github-actions]

🟢 2025-02-19 17:29:31 UTC The validation of the Pull Request description is successful.

[github-actions]

⚪ 2025-02-19 17:30:31 UTC Pre-commit check linux-x86_64-release-asan for 48237c2 has started.
⚪ 2025-02-19 17:30:59 UTC Artifacts will be uploaded here
⚪ 2025-02-19 17:34:09 UTC ya make is running...
🟡 2025-02-19 18:31:15 UTC Some tests failed, follow the links below. This fail is not in blocking policy yet Going to retry failed tests...

Details

Test history | Ya make output | Test bloat

TESTS	PASSED	ERRORS	FAILED	SKIPPED	MUTED?
11838	11767	0	18	19	34

⚪ 2025-02-19 18:32:30 UTC ya make is running... (failed tests rerun, try 2)
🟢 2025-02-19 18:44:34 UTC Tests successful.

Test history | Ya make output | Test bloat | Test bloat

TESTS	PASSED	ERRORS	FAILED	SKIPPED	MUTED?
107 (only retried tests)	72	0	0	5	30

🟢 2025-02-19 18:44:42 UTC Build successful.
🟢 2025-02-19 18:45:08 UTC ydbd size 3.6 GiB changed* by -16 Bytes, which is <= 0 Bytes vs main: OK

ydbd size dash	main: 81fbe15	merge: 48237c2	diff	diff %
ydbd size	3 894 662 984 Bytes	3 894 662 968 Bytes	-16 Bytes	-0.000%
ydbd stripped size	1 363 541 088 Bytes	1 363 541 088 Bytes	0 Bytes	0.000%

^{*please be aware that the difference is based on comparing your commit and the last completed build from the post-commit, check comparation}

[github-actions]

⚪ 2025-02-19 17:32:09 UTC Pre-commit check linux-x86_64-relwithdebinfo for 48237c2 has started.
⚪ 2025-02-19 17:32:27 UTC Artifacts will be uploaded here
⚪ 2025-02-19 17:35:22 UTC ya make is running...
🟡 2025-02-19 18:28:11 UTC Some tests failed, follow the links below. Going to retry failed tests...

Details

Test history | Ya make output | Test bloat

TESTS	PASSED	ERRORS	FAILED	SKIPPED	MUTED?
19150	17795	0	1	1217	137

⚪ 2025-02-19 18:30:00 UTC ya make is running... (failed tests rerun, try 2)
🟢 2025-02-19 18:48:39 UTC Tests successful.

Test history | Ya make output | Test bloat | Test bloat

TESTS	PASSED	ERRORS	FAILED	SKIPPED	MUTED?
209 (only retried tests)	76	0	0	2	131

🟢 2025-02-19 18:48:46 UTC Build successful.
🟢 2025-02-19 18:49:06 UTC ydbd size 2.1 GiB changed* by +16 Bytes, which is < 100.0 KiB vs main: OK

ydbd size dash	main: 81fbe15	merge: 48237c2	diff	diff %
ydbd size	2 238 945 856 Bytes	2 238 945 872 Bytes	+16 Bytes	+0.000%
ydbd stripped size	474 411 512 Bytes	474 411 512 Bytes	0 Bytes	0.000%

^{*please be aware that the difference is based on comparing your commit and the last completed build from the post-commit, check comparation}