Fix getErrors() for validation with redirect

[michalsn]

Description
When performing redirect _ci validation_errors session variable is not passed correctly.
Sadly this one is hard to test since we check ! is_cli() a couple of lines before.

Checklist:

• Securely signed commits
• Component(s) with PHPdocs
• Unit testing, with >80% coverage
• User guide updated
• Conforms to style guide

[MGatner]

I’ve actually been wondering if is_cli() should exempt testing. I’ve been doing that myself quite a bit.

[michalsn]

There is a risk that this may affect tests - but I don't know how much (if any).

[MGatner]

Seeing as how this is pretty much a typo I'm going with the change. Tests are good at the moment and if we need to adjust it is likely something that was wrong anyways.