Fixed storing and loading nulls and booleans in Redis

See #1311 

- [ ] Fix `LuaScriptBuilder` to use `HEXISTS` in case of `null` values instead of comparison.
- [x] Fix `LuaScriptBuilder` to cast booleans to 0 or 1 before using these in conditions.
I see. Then perhaps we should fill  the nulls as did here. But please double check again.