Remove inverted logic

[ValdasK]

Get rid of all inverted logic in controllers, where returns happen in case of failure, not success.

Current implementation requires code duplication and is prone to errors.

[l3pp4rd]

I do not see anything evil here, preventing nested if statements in deep levels is less complex in my opinion.. if I understand correctly the issue stated

[ValdasK]

If view you are rendering requires multiple parameters, controllers have plenty of duplication.

White-listing is easier to maintain than black-listing, because undefined cases default to error instead of success.

[l3pp4rd]

My point is that nesting if statements increases complexity and that is a fact. I cannot agree that it would be less complex otherwise. if your code needs more parameters, rearrange it the way you want.
Repeating code in most of the cases, does not increase complexity. Instead DRY sometimes also increases complexity. Making easy instead of making it simple increases complexity, not other way around