bug #34024 [Routing] fix route loading with wildcard, but dir or file is empty (gseidel)

This PR was merged into the 4.3 branch.

Discussion
----------

[Routing] fix route loading with wildcard, but dir or file is empty

| Q             | A
| ------------- | ---
| Branch?       |  4.3
| Bug fix?      | yes
| New feature?  | no
| Deprecations? | no
| Tickets       | no ticket i see so far
| License       | MIT

In my route config i have something like:

```yaml
empty_wildcard:
    resource: ../controller/empty_wildcard/*
    prefix: /empty_wildcard
```

But ``empty_wildcard`` is empty or has no route configured.

So i had this error:

``Call to a member function addPrefix() on null``

This PR take care if no route is configured, there will be no error.

Commits
-------

217058b475 [Routing] fix route loading with wildcard, but dir or file is empty

Author: nicolas-grekas

Loader/Configurator/RoutingConfigurator.php

@@ -39,7 +39,8 @@ public function __construct(RouteCollection $collection, PhpFileLoader $loader,
     final public function import($resource, $type = null, $ignoreErrors = false)
     {
         $this->loader->setCurrentDir(\dirname($this->path));
-        $imported = $this->loader->import($resource, $type, $ignoreErrors, $this->file);
+        $imported = $this->loader->import($resource, $type, $ignoreErrors, $this->file) ?: [];
+
         if (!\is_array($imported)) {
             return new ImportConfigurator($this->collection, $imported);
         }

Loader/XmlFileLoader.php

@@ -146,7 +146,8 @@ protected function parseImport(RouteCollection $collection, \DOMElement $node, $
 
         $this->setCurrentDir(\dirname($path));
 
-        $imported = $this->import($resource, ('' !== $type ? $type : null), false, $file);
+        /** @var RouteCollection[] $imported */
+        $imported = $this->import($resource, ('' !== $type ? $type : null), false, $file) ?: [];
 
         if (!\is_array($imported)) {
             $imported = [$imported];

Loader/YamlFileLoader.php

@@ -158,7 +158,7 @@ protected function parseImport(RouteCollection $collection, array $config, $path
 
         $this->setCurrentDir(\dirname($path));
 
-        $imported = $this->import($config['resource'], $type, false, $file);
+        $imported = $this->import($config['resource'], $type, false, $file) ?: [];
 
         if (!\is_array($imported)) {
             $imported = [$imported];