bug #6070 Fix cache warmer for empty controllers (javiereguiluz)

This PR was merged into the 4.x branch.

Discussion
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Fix cache warmer for empty controllers

Commits
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c880842 Fix cache warmer for empty controllers

src/Cache/CacheWarmer.php

@@ -47,6 +47,11 @@ public function warmUp(string $cacheDir, ?string $buildDir = null): array
             }
 
             $controller = u($controller);
+            if ($controller->isEmpty()) {
+                // this happens e.g. when using 'lexik/jwt-authentication-bundle', which defines an empty controller
+                continue;
+            }
+
             if (!$controller->endsWith('::index') && !$controller->endsWith('::__invoke')) {
                 continue;
             }