Fix PHP 8.5 deprecations

[nufue]

• bug fix
• BC break? no

Fixes two deprecation notices that appear when using dibi (v5.1.0) in PHP 8.5:

• Result.php::normalize(): Using null as an array offset is deprecated, use an empty string instead

• Row.php::getIterator(): ArrayIterator::__construct(): Using an object as a backing array for ArrayIterator is deprecated, as it allows violating class constraints and invariants