[Validator] Ensure numeric subpaths do not cause errors on PHP 7.4

Author: alexpott

src/Symfony/Component/Validator/Tests/Util/PropertyPathTest.php

@@ -32,6 +32,7 @@ public function provideAppendPaths()
             ['foo', 'bar', 'foo.bar', 'It append the subPath to the basePath'],
             ['foo', '[bar]', 'foo[bar]', 'It does not include the dot separator if subPath uses the array notation'],
             ['0', 'bar', '0.bar', 'Leading zeros are kept.'],
+            ['0', 1, '0.1', 'Numeric subpaths do not cause PHP 7.4 errors.'],
         ];
     }
 }

src/Symfony/Component/Validator/Util/PropertyPath.php

@@ -36,12 +36,13 @@ class PropertyPath
      */
     public static function append($basePath, $subPath)
     {
-        if ('' !== (string) $subPath) {
+        $subPath = (string) $subPath;
+        if ('' !== $subPath) {
             if ('[' === $subPath[0]) {
                 return $basePath.$subPath;
             }
 
-            return '' !== (string) $basePath ? $basePath.'.'.$subPath : $subPath;
+            return '' !== $basePath ? $basePath.'.'.$subPath : $subPath;
         }
 
         return $basePath;