Fix Model::__call throwing BadMethodCallException on empty results

* fix: fixed builder method call when fail parent::__call.

* test: add test for Model::AffectedRows.

* style: ./vendor/bin/php-cs-fixer fix --verbose --diff

* docs: fix issue link.

* refactor: I made sure not to call magic method in the parent class.

* style: composer cs-fix

* style: removed unnecessary variable.

* docs: $this|null -> mixed

system/Model.php

@@ -710,24 +710,19 @@ public function __isset(string $name): bool
      * Provides direct access to method in the builder (if available)
      * and the database connection.
      *
-     * @return $this|null
+     * @return mixed
      */
     public function __call(string $name, array $params)
     {
-        $result = parent::__call($name, $params);
+        $builder = $this->builder();
+        $result  = null;
 
-        if ($result === null && method_exists($builder = $this->builder(), $name)) {
+        if (method_exists($this->db, $name)) {
+            $result = $this->db->{$name}(...$params);
+        } elseif (method_exists($builder, $name)) {
             $result = $builder->{$name}(...$params);
-        }
-
-        if (empty($result)) {
-            if (! method_exists($this->builder(), $name)) {
-                $className = static::class;
-
-                throw new BadMethodCallException('Call to undefined method ' . $className . '::' . $name);
-            }
-
-            return $result;
+        } else {
+            throw new BadMethodCallException('Call to undefined method ' . static::class . '::' . $name);
         }
 
         if ($result instanceof BaseBuilder) {

tests/system/Models/AffectedRowsTest.php

@@ -0,0 +1,35 @@
+<?php
+
+/**
+ * This file is part of CodeIgniter 4 framework.
+ *
+ * (c) CodeIgniter Foundation <[email protected]>
+ *
+ * For the full copyright and license information, please view
+ * the LICENSE file that was distributed with this source code.
+ */
+
+namespace CodeIgniter\Models;
+
+use Tests\Support\Models\UserModel;
+
+/**
+ * @internal
+ */
+final class AffectedRowsTest extends LiveModelTestCase
+{
+    /**
+     * @see https://github.com/codeigniter4/CodeIgniter4/issues/5137
+     */
+    public function testAffectedRowsWithEmptyUpdate(): void
+    {
+        $this->createModel(UserModel::class);
+        $notExistsId = -1;
+        $this->model
+            ->set('country', 'US')
+            ->where('id', $notExistsId)
+            ->update();
+
+        $this->assertSame(0, $this->model->affectedRows());
+    }
+}