minor #24172 [FrameworkBundle] Enable assets with templates only if the Asset component is installed (hason)

This PR was merged into the 3.4 branch.

Discussion
----------

[FrameworkBundle] Enable assets with templates only if the Asset component is installed

| Q             | A
| ------------- | ---
| Branch?       | 3.4
| Bug fix?      | no
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets |
| License       | MIT
| Doc PR        | -

Commits
-------

5bc0b0527e [FrameworkBundle] Enable assets with templates only if the Asset component is installed

Author: fabpot

DependencyInjection/Configuration.php

@@ -52,7 +52,7 @@ public function getConfigTreeBuilder()
 
         $rootNode
             ->beforeNormalization()
-                ->ifTrue(function ($v) { return !isset($v['assets']) && isset($v['templating']); })
+                ->ifTrue(function ($v) { return !isset($v['assets']) && isset($v['templating']) && class_exists(Package::class); })
                 ->then(function ($v) {
                     $v['assets'] = array();