CI 4.18 -> 4.20 causes RouterException

Sorry, it seems a bug.
'\App\Controllers\backend\Dashboard::index' should work.

---

Can you try this patch?

Code:

--- a/system/Router/RouteCollection.php
+++ b/system/Router/RouteCollection.php
@@ -1008,7 +1008,7 @@ class RouteCollection implements RouteCollectionInterface
        $namespace = trim($this->defaultNamespace, '\\') . '\\';
        if (
            substr($search, 0, 1) !== '\\'
-            || substr($search, 0, strlen($namespace)) !== $namespace
+            && substr($search, 0, strlen($namespace)) !== $namespace
        ) {
            $search = $namespace . $search;
        }

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