Merge branch 'feature/php-di-7-service-locator' into mod7-merged

Author: partikus

src/Definition/Reference.php

@@ -54,7 +54,7 @@ public function getTargetEntryName() : string
     /**
      * Returns the name of the entity requesting this entry.
      */
-    public function getRequestingName() : string
+    public function getRequestingName() : ?string
     {
         return $this->requestingName;
     }