Fix phpstan

Author: samsonasik

rules/DowngradePhp82/Rector/FuncCall/DowngradeIteratorCountToArrayRector.php

@@ -17,6 +17,7 @@
 use Rector\Rector\AbstractRector;
 use Symplify\RuleDocGenerator\ValueObject\CodeSample\CodeSample;
 use Symplify\RuleDocGenerator\ValueObject\RuleDefinition;
+use Webmozart\Assert\Assert;
 
 /**
  * @changelog https://www.php.net/manual/en/migration82.other-changes.php#migration82.other-changes.functions.spl
@@ -90,6 +91,8 @@ public function refactor(Node $node): ?Node
             return null;
         }
 
+        Assert::isInstanceOf($node->args[0], Arg::class);
+
         $firstValue = $node->args[0]->value;
         $node->args[0]->value = new Ternary(
             $this->nodeFactory->createFuncCall('is_array', [new Arg($firstValue)]),