fix(util/timer): fix valgrind warning
fix(util/timer): fix valgrind warning

fpvandoorn/lean,leanprover-community/lean,johoelzl/lean,leodemoura/lean,Kha/lean,rlewis1988/lean,digama0/lean,leodemoura/lean,digama0/lean,leanprover-community/lean,avigad/lean,dselsam/lean,fpvandoorn/lean,avigad/lean,Kha/lean,avigad/lean,johoelzl/lean,leanprover-community/lean,leanprover/lean,dselsam/lean,leanprover-community/lean,fpvandoorn/lean,leanprover/lean,leanprover-community/lean,leanprover/lean,avigad/lean,rlewis1988/lean,digama0/lean,johoelzl/lean,rlewis1988/lean,rlewis1988/lean,digama0/lean,Kha/lean,Kha/lean,johoelzl/lean,leanprover/lean,fpvandoorn/lean,fpvandoorn/lean,johoelzl/lean,dselsam/lean,leanprover/lean,rlewis1988/lean,rlewis1988/lean,avigad/lean,dselsam/lean,avigad/lean,johoelzl/lean,leodemoura/lean,leanprover-community/lean,leodemoura/lean,dselsam/lean,dselsam/lean,Kha/lean,digama0/lean,Kha/lean,leodemoura/lean,digama0/lean,leanprover/lean,leodemoura/lean,fpvandoorn/lean