[Validator] Fix fields without constraints in Collection

Author: HypeMC

src/Symfony/Component/Validator/Constraints/Collection.php

@@ -94,20 +94,20 @@ private static function isFieldsOption($options): bool
             return false;
         }
 
-        if ([] === $options) {
-            return true;
-        }
-
         foreach ($options as $optionOrField) {
             if ($optionOrField instanceof Constraint) {
                 return true;
             }
 
+            if (null === $optionOrField) {
+                continue;
+            }
+
             if (!\is_array($optionOrField)) {
                 return false;
             }
 
-            if ([] !== $optionOrField && !($optionOrField[0] ?? null) instanceof Constraint) {
+            if ($optionOrField && !($optionOrField[0] ?? null) instanceof Constraint) {
                 return false;
             }
         }

src/Symfony/Component/Validator/Tests/Constraints/CollectionTest.php

@@ -175,10 +175,15 @@ public function testEmptyFieldsInOptions()
         $this->assertSame('foo bar baz', $constraint->extraFieldsMessage);
     }
 
-    public function testEmptyConstraintListFor()
+    /**
+     * @testWith [[]]
+     *           [null]
+     */
+    public function testEmptyConstraintListForField(?array $fieldConstraint)
     {
-        $constraint = new Collection([
-                'foo' => [],
+        $constraint = new Collection(
+            [
+                'foo' => $fieldConstraint,
             ],
             null,
             null,
@@ -193,11 +198,15 @@ public function testEmptyConstraintListFor()
         $this->assertSame('foo bar baz', $constraint->extraFieldsMessage);
     }
 
-    public function testEmptyConstraintListForFieldInOptions()
+    /**
+     * @testWith [[]]
+     *           [null]
+     */
+    public function testEmptyConstraintListForFieldInOptions(?array $fieldConstraint)
     {
         $constraint = new Collection([
             'fields' => [
-                'foo' => [],
+                'foo' => $fieldConstraint,
             ],
             'allowExtraFields' => true,
             'extraFieldsMessage' => 'foo bar baz',