Fix null error when using with SSG

[lokmanm]

When using SEO Pro with Statamic SSG, and you have a custom route:

Route::statamic('/custom', 'pages.custom', [
    'seo' => [
        'title' => 'Custom Title',
        'description' => 'Custom Description',
    ]
]);

For some reason $this->current on the parseAntlers function returns null which throws an error during builds.

[ryanmitchell]

I came here to open a PR for the same thing, seems the code has changed since you opened this, so I've a new PR at #381

[duncanmcclean]

Thanks for this! Closing in favour of #381.

[jesseleite]

Yes thank you @lokmanm! Sorry for the delay. Just tagged the fix in 6.6.4 🤘