[Bug Fix] Ability to check for records in sqlite DB using NULL

This is a copy of the fix applied to the MySQL driver, but needs to be applied here to allow it to fix sqlite.

https://github.com/Codeception/Codeception/commit/9467f61c97bc23c2a5b35ff4f89deb26f10ab1fc
Merge pull request #1076 from TheShiftExchange/patch-1

[Bug Fix] Ability to check for records in sqlite DB using NULL