Fixed issue #267: PHP warnings about margins in helper.php.

[nerun]

PHP Warning:  Undefined array key "padding-left" in .../public_html/wiki/lib/plugins/wrap/helper.php on line 398
PHP Warning:  Undefined array key "margin-left" in .../public_html/wiki/lib/plugins/wrap/helper.php on line 466
PHP Warning:  Undefined array key "margin-right" in .../public_html/wiki/lib/plugins/wrap/helper.php on line 467
PHP Warning:  Undefined array key "margin-top" in .../public_html/wiki/lib/plugins/wrap/helper.php on line 468
PHP Warning:  Undefined array key "margin-bottom" in .../public_html/wiki/lib/plugins/wrap/helper.php on line 469

• Using master branch, not the package from dokuwiki.
• PHP 8.1 here.

[fiwswe]

Wouldn't it be easier and shorter to use the Null Coalescing Operator here?

E.g. instead of:

        if ( isset($properties ['margin-left']) ) {
            $properties ['padding-left'] = $properties ['margin-left'];
        } else {
            $properties ['padding-left'] = null;
        }

the same functionality can be expressed as:

        $properties ['padding-left'] = $properties ['margin-left'] ?? null;

[nerun]

Thank you, i am very new in php.