Fix UBSan report while compiling with clang-18

[alexey-milovidov]

This is a benign report. But clang-18 started to complain.

See https://github.com/ClickHouse/ClickHouse/issues/63858

[coveralls]

Pull Request Test Coverage Report for Build 9103733837

Details

• 1 of 1 (100.0%) changed or added relevant line in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 98.964%

---

Totals
Change from base Build 9038987381:	0.0%
Covered Lines:	16427
Relevant Lines:	16599

---

💛 - Coveralls

[jmalkin]

This makes sense. I don't think the existing code is unsafe, but UBSan has trouble determining that and (validly) complains.