handle null Engine in CS schema

[swalrus1]

• handle null Engine in CS schema
• Update schema.cpp

Changelog entry

...

Changelog category

• Not for changelog (changelog entry is not required)

Description for reviewers

...

[github-actions]

⚪ 2025-03-25 18:45:31 UTC Pre-commit check for 341000a has started.
⚪ 2025-03-25 18:48:15 UTC Build linux-x86_64-relwithdebinfo is running...
🟢 2025-03-25 19:28:04 UTC Build successful.
⚪ 2025-03-25 19:28:22 UTC Tests are running...
🔴 2025-03-25 21:20:56 UTC Some tests failed, follow the links below.

Test history | Test log

TESTS	PASSED	ERRORS	FAILED	SKIPPED	MUTED?
39133	33855	0	19	5217	42

🟢 2025-03-25 21:21:53 UTC ydbd size 8.3 GiB changed* by -616 Bytes, which is <= 0 Bytes vs stable-24-4: OK

ydbd size dash	stable-24-4: 07e7130	merge: 341000a	diff	diff %
ydbd size	8 898 201 592 Bytes	8 898 200 976 Bytes	-616 Bytes	-0.000%
ydbd stripped size	485 015 464 Bytes	485 015 400 Bytes	-64 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]

⚪ 2025-03-25 18:47:35 UTC Pre-commit check for 341000a has started.
⚪ 2025-03-25 18:50:15 UTC Build linux-x86_64-release-asan is running...
🟢 2025-03-25 19:13:52 UTC Build successful.
⚪ 2025-03-25 19:14:08 UTC Tests are running...
🔴 2025-03-25 21:22:57 UTC Some tests failed, follow the links below.

Test history | Test log

TESTS	PASSED	ERRORS	FAILED	SKIPPED	MUTED?
10459	10351	0	35	29	44

🟢 2025-03-25 21:23:51 UTC ydbd size 5.6 GiB changed* by -880 Bytes, which is <= 0 Bytes vs stable-24-4: OK

ydbd size dash	stable-24-4: 07e7130	merge: 341000a	diff	diff %
ydbd size	6 027 596 904 Bytes	6 027 596 024 Bytes	-880 Bytes	-0.000%
ydbd stripped size	1 508 432 480 Bytes	1 508 431 776 Bytes	-704 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}