BUGFIX: Use "useCustomErrorView()" method in exception handler

Flow versions prior to 6.3.16 would render static exceptions
when "templatePathAndFilename" was null. Since 6.3.16, Flow
only checks if the array key is set, which it is in our case.

Classes/Handler/ProductionExceptionHandler.php

@@ -67,4 +67,14 @@ protected function findErrorPageConfigurationForRequest(int $statusCode)
         );
     }
 
+    /**
+     * Override new method introduced in Flow 6.3.16
+     *
+     * @return bool
+     */
+    protected function useCustomErrorView(): bool
+    {
+        return false;
+    }
+
 }

Configuration/Settings.yaml

@@ -3,11 +3,6 @@ Neos:
     error:
       exceptionHandler:
         renderingGroups:
-          notFoundExceptions:
-            options:
-              # Force static exception rendering.
-              templatePathAndFilename: null
-              viewClassName: Neos\FluidAdaptor\View\StandaloneView
           serverErrorExceptions:
             matchingStatusCodes: [ 500 ]
             options: