[Validator] Fix type error for non-array items when Unique::fields is set

Author: aprat84

Constraints/UniqueValidator.php

@@ -45,7 +45,7 @@ public function validate(mixed $value, Constraint $constraint)
         foreach ($value as $element) {
             $element = $normalizer($element);
 
-            if ($fields && !$element = $this->reduceElementKeys($fields, $element)) {
+            if ($fields && !(\is_array($element) && $element = $this->reduceElementKeys($fields, $element))) {
                 continue;
             }
 

Tests/Constraints/UniqueValidatorTest.php

@@ -243,6 +243,30 @@ public static function getInvalidFieldNames(): array
         ];
     }
 
+    /**
+     * @dataProvider getValidCollectionValues
+     */
+    public function testValidCollectionValues(array $value, array $fields)
+    {
+        $this->validator->validate($value, new Unique(fields: $fields));
+
+        $this->assertNoViolation();
+    }
+
+    public static function getValidCollectionValues(): array
+    {
+        return [
+            'unique empty item' => [
+                [['field' => 1], ['field' => 2], []],
+                ['field'],
+            ],
+            'unique non-array item' => [
+                [['field' => 1], ['field' => 2], '', 1, null],
+                ['field'],
+            ],
+        ];
+    }
+
     /**
      * @dataProvider getInvalidCollectionValues
      */