[Php74] Fix isset guard never converting on IfToNullCoalescingAssignRector

[Soean]

The non-nullable property skip from #8387 reads the type off the fetch node returned by matchNullGuardedExpr(). For the ! isset($prop) form that node sits inside Isset_, where PHPStan has already narrowed null out of the type. TypeCombinator::containsNull() is therefore always false, isNonNullableProperty() always returns true, and the skip fires for every property under isset, nullable or not.

Before (same nullable property, three guard forms)

class Demo
{
    private ?array $values = null;

    public function get(): array
    {
        // skipped, but should convert
        if (! isset($this->values)) {
            $this->values = ['default'];
        }

        // converts
        if (null === $this->values) {
            $this->values = ['default'];
        }

        // converts
        if (is_null($this->values)) {
            $this->values = ['default'];
        }

        return $this->values;
    }
}

Only the isset form is affected, so it was silently disabled for properties, including the case the rule advertises in its CodeSample.

Fix

Resolve the declared type through ReflectionResolver::resolvePropertyReflectionFromPropertyFetch() instead of nodeTypeResolver->getType() on the fetch node. getReadableType() stays phpdoc-aware like the previous call, but carries no scope narrowing.

After

// nullable property, isset form
$this->values ??= ['default'];

skip_typed_non_nullable_property.php.inc keeps skipping, so the boundary #8387 intended is unchanged, the two fixtures now pin it from both sides.

[samsonasik]

looks good

[TomasVotruba]

Thank you