Fix segfault when UserToken == nullptr

[UgnineSirdis]

(cherry picked from commit 52d9c30)

Changelog entry

Fix segfault that appeared after 6576464 (#5982)

In code that was before the bug there was no case when execution reaches the point Handle(TEvAuthorizeTicketResult) with Token == nullptr

https://github.com/ydb-platform/ydb/blob/e791eb9a768ec51b5ca478c2aff5236a22ed67b8/ydb/core/mon/mon.cpp - DefaultAuthorizer

https://github.com/ydb-platform/ydb/blob/e791eb9a768ec51b5ca478c2aff5236a22ed67b8/ydb/core/mon/async_http_mon.cpp - we get nullptr in Authorizer and execute SendRequest() without check

Changelog category

• Bugfix

Additional information

...

[github-actions]

⚪ 2024-08-15 14:29:28 UTC Pre-commit check for b623341 has started.
⚪ 2024-08-15 14:32:25 UTC Build linux-x86_64-release-clang14 is running...
🟢 2024-08-15 14:49:14 UTC Build successful.

[github-actions]

⚪ 2024-08-15 18:32:03 UTC Pre-commit check for b623341 has started.
⚪ 2024-08-15 18:34:37 UTC Build linux-x86_64-relwithdebinfo is running...
🟢 2024-08-15 19:11:17 UTC Build successful.
⚪ 2024-08-15 19:11:32 UTC Tests are running...
🔴 2024-08-15 20:55:08 UTC Some tests failed, follow the links below.

Test history | Test log

TESTS	PASSED	ERRORS	FAILED	SKIPPED	MUTED?
39050	33823	0	2	5214	11

🟢 2024-08-15 20:55:48 UTC ydbd size 8.1 GiB changed* by +128 Bytes, which is < 100.0 KiB vs stable-24-3: OK

ydbd size dash	stable-24-3: aa5a493	merge: b623341	diff	diff %
ydbd size	8 724 005 880 Bytes	8 724 006 008 Bytes	+128 Bytes	+0.000%
ydbd stripped size	476 920 584 Bytes	476 920 584 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]

⚪ 2024-08-15 14:47:40 UTC Pre-commit check for b623341 has started.
⚪ 2024-08-15 14:50:12 UTC Build linux-x86_64-release-asan is running...
🟢 2024-08-15 15:13:27 UTC Build successful.
⚪ 2024-08-15 15:13:42 UTC Tests are running...
🔴 2024-08-15 18:02:23 UTC Some tests failed, follow the links below.

Test history | Test log

TESTS	PASSED	ERRORS	FAILED	SKIPPED	MUTED?
10513	10464	0	12	24	13

🟢 2024-08-15 18:02:53 UTC ydbd size 5.5 GiB changed* by +384 Bytes, which is < 100.0 KiB vs stable-24-3: OK

ydbd size dash	stable-24-3: aa5a493	merge: b623341	diff	diff %
ydbd size	5 904 370 648 Bytes	5 904 371 032 Bytes	+384 Bytes	+0.000%
ydbd stripped size	1 480 261 344 Bytes	1 480 261 344 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}