use the empty string instead of null as an array offset

Author: xabbuh

DependencyInjection/TranslatorPathsPass.php

@@ -96,10 +96,10 @@ protected function processValue(mixed $value, bool $isRoot = false): mixed
                     $class = $this->definitions[$i]->getClass();
 
                     if (ServiceLocator::class === $class) {
-                        if (!isset($this->controllers[$this->currentId])) {
+                        if (!isset($this->controllers[$this->currentId ?? ''])) {
                             continue;
                         }
-                        foreach ($this->controllers[$this->currentId] as $class => $_) {
+                        foreach ($this->controllers[$this->currentId ?? ''] as $class => $_) {
                             $this->paths[$class] = true;
                         }
                     } else {