bug #10119 [Validator] Minor fix in XmlFileLoader (florianv)

This PR was merged into the 2.3 branch.

Discussion
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[Validator] Minor fix in XmlFileLoader

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets |
| License       | MIT
| Doc PR        |

An instance of `\SimpleXMLElement` is passed to the `newConstraint` method instead of a string which can lead to weird type juggling issues.

Commits
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16b726c [Validator] Minor fix in XmlLoader

src/Symfony/Component/Validator/Mapping/Loader/AbstractLoader.php

@@ -36,10 +36,10 @@ abstract class AbstractLoader implements LoaderInterface
     /**
      * Creates a new constraint instance for the given constraint name.
      *
-     * @param string $name The constraint name. Either a constraint relative
-     *                        to the default constraint namespace, or a fully
-     *                        qualified class name
-     * @param array $options The constraint options
+     * @param string $name   The constraint name. Either a constraint relative
+     *                       to the default constraint namespace, or a fully
+     *                       qualified class name
+     * @param mixed $options The constraint options
      *
      * @return Constraint
      *

src/Symfony/Component/Validator/Mapping/Loader/XmlFileLoader.php

@@ -105,7 +105,7 @@ class XmlFileLoader extends FileLoader
                 $options = null;
             }
 
-            $constraints[] = $this->newConstraint($node['name'], $options);
+            $constraints[] = $this->newConstraint((string) $node['name'], $options);
         }
 
         return $constraints;