Misleading error message

[I ran into a problem](https://github.com/getgrav/grav/pull/2121) where the error message was quite unhelpful. [Here](https://github.com/getgrav/grav-plugin-admin/blob/b77d0e6053fd432eb59a5cd2ed503ab64d1f90b6/classes/adminbasecontroller.php#L138) is the specific code:

```
protected function validateNonce()
{
if (strtolower($_SERVER['REQUEST_METHOD']) === 'post') {
if (isset($this->post['admin-nonce'])) {
$nonce = $this->post['admin-nonce'];
} else {
$nonce = $this->grav['uri']->param('admin-nonce');
}

if (!$nonce || !Utils::verifyNonce($nonce, 'admin-form')) {
if ($this->task === 'addmedia') {

$message = sprintf($this->admin->translate('PLUGIN_ADMIN.FILE_TOO_LARGE', null),
ini_get('post_max_size'));
[...]
```

It seems to me that the function is not related to the file size of uploaded images. We don't check the file size . What we really check is if the nonce (token) is valid or not. Why is there an extra condition for the `addmedia` task? Is this intentional?

Start in classes/adminbasecontroller.php at validateNonce(), especially the addmedia branch and its call to Utils::verifyNonce(). Trace how the admin-nonce is obtained and how FILE_TOO_LARGE is presented. Done means clarifying whether the addmedia condition is intentional and correcting the misleading message or behavior, with the relevant validation flow still covered.

Written by the indexing model from the issue text.