fix: when $credentials is empty array

Author: kenjis

src/Models/UserModel.php

@@ -177,6 +177,10 @@ public function findByCredentials(array $credentials): ?User
         $email = $credentials['email'] ?? null;
         unset($credentials['email']);
 
+        if ($email === null && $credentials === []) {
+            return null;
+        }
+
         // any of the credentials used should be case-insensitive
         foreach ($credentials as $key => $value) {
             $this->where(

tests/Unit/UserModelTest.php

@@ -48,14 +48,16 @@ public function testSaveInsertUser(): void
     /**
      * @see https://github.com/codeigniter4/shield/issues/546
      */
-    public function testfindByCredentialsEmailEmptyString(): void
+    public function testfindByCredentialsEmptyEmail(): void
     {
         $users = $this->createUserModel();
         $user  = $this->createNewUser();
         $users->save($user);
 
         $user = $users->findByCredentials(['email' => '']);
+        $this->assertNull($user);
 
+        $user = $users->findByCredentials([]);
         $this->assertNull($user);
     }