MDEV-34621: Fix division by zero in mariadb-slap when iterations=0

[KhaledR57]

• The Jira issue number for this PR is: MDEV-34621

Description

mariadb-slap crashes with a floating point exception when run with -i0 due to division by zero in generate_stats(). This occurs when calculating average timing by dividing by the number of iterations.
Instead of modifying the minimum value for the -i option (which would cause unexpected warning messages even with valid values), this PR implements a targeted fix in the generate_stats(). The solution checks if iterations == 0 before performing the division, and in such cases, returns early from the function.

Release Notes

Fixed a floating point exception (division by zero) crash in mariadb-slap when running with -i0 (zero iterations).

How can this PR be tested?

This PR can be tested by manually running mariadb-slap with zero iterations, which would previously cause a crash:

$ mariadb-slap -i0 --only-print

Or

$ ./mtr main.mysqlslap

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.

[svoj]

Please add a test case and amend your fix.

[svoj]

Adjust commit comment according to https://github.com/MariaDB/server/blob/11.0/CODING_STANDARDS.md

That is split long lines. Sentences should end with period.

Could you also retarget it for 10.6? Or I can do it myself once PR is approved.

[CLAassistant]

All committers have signed the CLA.