Исправить баг attempt to perform arithmetic on a boolean value

В zsetKeysMemoryUsage.lua скрипте что то не преобразуется в число, а в булев тип, возможно какой-то вызов возвращает nil.

Start by inspecting zsetKeysMemoryUsage.lua and tracing the values used in its arithmetic expression. Reproduce the reported boolean-value error, identify whether the relevant call returns a boolean or nil, and verify that the script handles the value numerically without changing the intended memory-usage result.

Written by the indexing model from the issue text.