grav.CRITICAL: Syntax error with Page Security tab - Page Groups

[Quitoboss]

I detected the following bug:
There is in Security tab of page configuration.
If you configure the "Page Groups" with no value or with a group but don't select any specific CRUD permisión when saving it brokes giving the next message:

Server Error
Sorry, something went terribly wrong!
4 - Syntax error
For further details please review your logs/ folder, or enable displaying of errors in your system configuration.

Then in grav.log yo will see:
grav.CRITICAL: Syntax error - Trace: #0 /var/www/vhosts/[...]/user/plugins/flex-objects/classes/Admin/AdminController.php(1861): json_decode('', true, 512, 4194304) #1

And 30 lines more.
8 about AdminController
4 about EventDispatcher
4 about Themes
10 about RequestHandler
etc.

This was found trying to figure out how can I configure a private page for users (With Grav Login Plugin)

Best regards

[pmoreno-rodriguez]

I confirm this error.
Some validation may be missing to prevent the responsible function from passing empty or null data.

(user/plugins/flex-objects/classes/Admin/AdminController.php1861)
I have not tried it. The following maybe works:

protected function jsonDecode(array $data)
     {
         foreach ($data as &$value) {
             if (!empty($value)) {
                 if (is_array($value)) {
                    $value = $this->jsonDecode($value);
                 } else {
                   $value = json_decode($value, true, 512, JSON_THROW_ON_ERROR);
                 }
             }
         }
 
         return $data;
     }