[NFC] fix comment blocks capitalising null

[eileenmcnaughton]

Overview

Code cleanup to comply with tighter coder standard

Before

@var string|NULL

After

@var string|null

Technical Details

From running the drupal code sniffer with type checking enabled it turns out the capitalisation of NULL
does not extend to docblocks.

See civicrm/coder#7

Comments

[civibot]

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[colemanw]

My personal opinion is that declaring @var string|null is pretty pointless, since null isn't actually a type and it's obviously going to be null until you put a string in it. What you want to know from the docblock is what type it's going to contain after a value is set, and no one really cares about the fact that an unset variable is null.

[eileenmcnaughton]

@colemanw possibly - but I'm not going to go through them one by one to check if they could be 'set-ish & still null' just to address a code formatting std

[colemanw]

My point is that, by definition, a variable is not set if it is null, and all |null type declarations are pointless.

[eileenmcnaughton]

I get that - but I'm not keen on including that in this scope