Fix typo in variable name.

This reverts commit 9ad60fe1.

Psalm is starting to get annoying. Both openssl_decrypt() and realpath() can return a string or false on error. Psalm seems to ignore the latter all of a sudden, so it assumes the returned variable will always be a string and then it fails when you check on errors. This fix explicitly declares the problematic variables with types string or false, so that psalm stops complaining.

MySQL key value store now handles NULL expiries.

Scrutinizer:
The expression $result of type array is implicitly converted to a boolean; are you sure this is intended? If so, consider using empty($expr) instead to make it clear that you intend to check for an array without elements.

setupTwigTemplatepaths() cannot return false