docs: fix incorrect @return type

Author: kenjis

system/Database/BaseResult.php

@@ -292,9 +292,15 @@ public function getRow($n = 0, string $type = 'object')
     /**
      * Returns a row as a custom class instance.
      *
-     * If row doesn't exists, returns null.
+     * If the row doesn't exist, returns null.
      *
-     * @return array|null
+     * @template T of object
+     *
+     * @param         int             $n         The row number of the results
+     * @phpstan-param class-string<T> $className
+     *
+     * @return         object|null
+     * @phpstan-return T|null
      */
     public function getCustomRowObject(int $n, string $className)
     {

system/Database/ResultInterface.php

@@ -69,9 +69,15 @@ public function getRow($n = 0, string $type = 'object');
     /**
      * Returns a row as a custom class instance.
      *
-     * If row doesn't exists, returns null.
+     * If the row doesn't exist, returns null.
      *
-     * @return array|null
+     * @template T of object
+     *
+     * @param         int             $n         The row number of the results
+     * @phpstan-param class-string<T> $className
+     *
+     * @return         object|null
+     * @phpstan-return T|null
      */
     public function getCustomRowObject(int $n, string $className);