Fix segfault when UserToken == nullptr

[UgnineSirdis]

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]

⚪ 2024-08-14 20:46:42 UTC Pre-commit check for 9f6861f has started.
⚪ 2024-08-14 20:49:43 UTC Check linux-x86_64-release-clang14 is running...
🟢 2024-08-14 20:54:59 UTC Build successful.

[github-actions]

⚪ 2024-08-14 20:46:51 UTC Pre-commit check for 9f6861f has started.
⚪ 2024-08-14 20:49:40 UTC Check linux-x86_64-relwithdebinfo is running...
🟡 2024-08-14 22:11:06 UTC Some tests failed, follow the links below. Going to retry failed tests...

Test history | Ya make output

TESTS	PASSED	ERRORS	FAILED	SKIPPED	MUTED?
39289	33943	0	3	5309	34

⚪ 2024-08-14 22:14:32 UTC Failed tests rerun (try 2) linux-x86_64-relwithdebinfo is running...
🟢 2024-08-14 22:21:40 UTC Tests successful.

Test history | Ya make output

TESTS	PASSED	ERRORS	FAILED	SKIPPED	MUTED?
49 (only retried tests)	20	0	0	0	29

🟢 2024-08-14 22:21:47 UTC Build successful.
🟢 2024-08-14 22:22:21 UTC ydbd size 8.1 GiB changed* by +112 Bytes, which is < 100.0 KiB vs main: OK

ydbd size dash	main: 3fc1bbf	merge: 9f6861f	diff	diff %
ydbd size	8 728 105 728 Bytes	8 728 105 840 Bytes	+112 Bytes	+0.000%
ydbd stripped size	474 469 896 Bytes	474 469 896 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 10:18:13 UTC Pre-commit check for 9f6861f has started.
⚪ 2024-08-15 10:21:13 UTC Check linux-x86_64-release-asan is running...
🔴 2024-08-15 12:32:12 UTC Some tests failed, follow the links below.

Test history | Ya make output

TESTS	PASSED	ERRORS	FAILED	SKIPPED	MUTED?
10456	10377	0	14	29	36

🟢 2024-08-15 12:33:08 UTC Build successful.
🟢 2024-08-15 12:33:35 UTC ydbd size 5.5 GiB changed* by +384 Bytes, which is < 100.0 KiB vs main: OK

ydbd size dash	main: 3fc1bbf	merge: 9f6861f	diff	diff %
ydbd size	5 879 741 568 Bytes	5 879 741 952 Bytes	+384 Bytes	+0.000%
ydbd stripped size	1 477 037 360 Bytes	1 477 037 360 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}