Add default empty array in constructor

This class its constructor argument `$tagGenerators` is empty by default in PHP, so that via DI argument types in `di.xml` files the array is filled automatically. This actually means that - without any runtime configuration of this argument - the PHP class has a required argument `$tagGenerators`.

In my cases, this is breaking DI compile when the modules `Magento_DirectoryGraphQl` and `Magento_StoreGraphQl` are disabled (and actually a lot of people will disable this module if they are not building a headless shop). This PR is a simple but required fix.

Author: jissereitsma

app/code/Magento/Store/Model/Config/Cache/Tag/Strategy/CompositeTagGenerator.php

@@ -23,7 +23,7 @@ class CompositeTagGenerator implements TagGeneratorInterface
      * @param TagGeneratorInterface[] $tagGenerators
      */
     public function __construct(
-        array $tagGenerators
+        array $tagGenerators = []
     ) {
         $this->tagGenerators = $tagGenerators;
     }