[Php74] Skip non-nullable typed property on IfToNullCoalescingAssignRector

[TomasVotruba]

IfToNullCoalescingAssignRector rewrites a null guard if into ??= without checking the target is nullable. When the target is a typed non-nullable property, the ??= left side can never be null, so PHPStan flags it:

Static property Foo::$parameters (array) on left side of ??= is not nullable — nullCoalesce.property

Before (rule fires, produces invalid code)

class TokenHelper
{
    private static array $parameters;

    public function get(): array
    {
        // rule turns this...
        if (! isset(self::$parameters)) {
            self::$parameters = ['default'];
        }

        return self::$parameters;
    }
}

// ...into this — PHPStan: left side of ??= is not nullable
self::$parameters ??= ['default'];

Fix

Skip when the guarded target is a PropertyFetch / StaticPropertyFetch with a declared non-nullable type. Untyped properties (MixedType) still convert as before.

After

// typed non-nullable property left unchanged
if (! isset(self::$parameters)) {
    self::$parameters = ['default'];
}