minor #21225 [DI] Dont share service when no id provided (nicolas-grekas)

This PR was merged into the 2.7 branch.

Discussion
----------

[DI] Dont share service when no id provided

| Q             | A
| ------------- | ---
| Branch?       | 2.7
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | -
| License       | MIT
| Doc PR        | -

Commits
-------

814f633 [DI] Dont share service when no id provided

Author: nicolas-grekas

ContainerBuilder.php

@@ -430,7 +430,7 @@ public function get($id, $invalidBehavior = ContainerInterface::EXCEPTION_ON_INV
         }
 
         if (!array_key_exists($id, $this->definitions) && isset($this->aliasDefinitions[$id])) {
-            return $this->get($this->aliasDefinitions[$id], $invalidBehavior);
+            return $this->get((string) $this->aliasDefinitions[$id], $invalidBehavior);
         }
 
         try {
@@ -1099,15 +1099,15 @@ private function callMethod($service, $call)
     /**
      * Shares a given service in the container.
      *
-     * @param Definition $definition
-     * @param mixed      $service
-     * @param string     $id
+     * @param Definition  $definition
+     * @param mixed       $service
+     * @param string|null $id
      *
      * @throws InactiveScopeException
      */
     private function shareService(Definition $definition, $service, $id)
     {
-        if (self::SCOPE_PROTOTYPE !== $scope = $definition->getScope()) {
+        if (null !== $id && self::SCOPE_PROTOTYPE !== $scope = $definition->getScope()) {
             if (self::SCOPE_CONTAINER !== $scope && !isset($this->scopedServices[$scope])) {
                 throw new InactiveScopeException($id, $scope);
             }