public function clearEmptyTokens()
    {
        $limit = $this->count();
        $index = 0;

        for (; $index < $limit; ++$index) {
            if ($this->isEmptyAt($index)) {
                break;
            }
        }

        // no empty token found, therefore there is no need to override collection
        if ($limit === $index) {
            return;
        }

        for ($count = $index; $index < $limit; ++$index) {
            if (!$this->isEmptyAt($index)) {
                $this[$count++] = $this[$index];
            }
        }

        $this->setSize($count);
    }