MDEV-35472 Server crash in ha_storage_put_memlim upon reading from INNODB_LOCKS

[dr-m]

• The Jira issue number for this PR is: MDEV-35472

Description

ha_storage_put_memlim(): Initialize node->next in order to avoid a crash on a subsequent invocation, due to dereferencing an uninitialized pointer.

This fixes a regression that had been introduced in #3584 (MDEV-35189).

Release Notes

Because the bug is being fixed in the same releases that introduce it, no mention is needed.

How can this PR be tested?

Apparently, this subsystem is badly covered by existing regression tests. It would be challenging to test this, because there is some rate-limiting of updates of the cache. This was tested with a small stress test using cmake -DWITH_ASAN=ON.

Basing the PR against the correct MariaDB version

• This is a new feature or a refactoring, and the PR is based against the main branch.
• This is a bug fix, and the PR is based against the earliest maintained branch in which the bug can be reproduced.

PR quality check

• I checked the CODING_STANDARDS.md file and my PR conforms to this where appropriate.
• For any trivial modifications to the PR, I am ok with the reviewer making the changes themselves.

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