[BUGFIX] Allow routes without actual route variables for ExtbaseEnhancer

The route configuration shown below using `ExtbaseEnhancer` is currently
not evaluated anymore due to missing route variables in `routePath`. For
this particular case in `ExtbaseEnhancer` the controller-action pair is
implicitly defining variables.

MyPlugin:
  type: Extbase
  extension: ...
  plugin: ...
  routes:
    -
      routePath: '/action'
      _controller: 'MyController::action'

Resolves: #91880
Releases: master, 10.4, 9.5
Change-Id: Ib42f87c3c9f83acc7f2ceec4a93169d15777ed08
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/65134


Tested-by: Markus Klein <markus.klein@typo3.org>
Tested-by: TYPO3com <noreply@typo3.com>
Tested-by: Marco Bresch <marco.bresch@starfinanz.de>
Tested-by: Georg Tiefenbrunn <georg.tiefenbrunn@gmail.com>
Tested-by: Oliver Hader <oliver.hader@typo3.org>
Reviewed-by: Markus Klein <markus.klein@typo3.org>
Reviewed-by: Georg Tiefenbrunn <georg.tiefenbrunn@gmail.com>
Reviewed-by: Oliver Hader <...

typo3/sysext/extbase/Classes/Routing/ExtbasePluginEnhancer.php

@@ -147,7 +147,9 @@ class ExtbasePluginEnhancer extends PluginEnhancer
             $variables = array_flip($compiledRoute->getPathVariables());
             $mergedParams = array_replace($variant->getDefaults(), $deflatedParameters);
             // all params must be given, otherwise we exclude this variant
-            if ($variables === [] || array_diff_key($variables, $mergedParams) !== []) {
+            // (it is allowed that $variables is empty - in this case variables are
+            // "given" implicitly through controller-action pair in `_controller`)
+            if (array_diff_key($variables, $mergedParams)) {
                 continue;
             }
             $variant->addOptions(['deflatedParameters' => $deflatedParameters]);