Fix PHPStan errors (#20603)

framework/db/BatchQueryResult.php

@@ -68,11 +68,11 @@ class BatchQueryResult extends Component implements \Iterator
     public $each = false;
 
     /**
-     * @var DataReader the data reader associated with this batch query.
+     * @var DataReader|null the data reader associated with this batch query.
      */
     private $_dataReader;
     /**
-     * @var array the data retrieved in the current batch
+     * @var array|null the data retrieved in the current batch
      */
     private $_batch;
     /**
@@ -80,7 +80,7 @@ class BatchQueryResult extends Component implements \Iterator
      */
     private $_value;
     /**
-     * @var string|int the key for the current iteration
+     * @var string|int|null the key for the current iteration
      */
     private $_key;
 

framework/db/sqlite/Command.php

@@ -71,7 +71,9 @@ class Command extends \yii\db\Command
      * or `false` if there's a single statement.
      * @param string $sql
      * @param array $params
-     * @return string[]|false
+     * @return array[]|false
+     *
+     * @phpstan-return list<array{string, array}>|false
      */
     private function splitStatements($sql, $params)
     {