plugin uninstall function drop the tables, but shows errors on admin

I'm new in Wordpress and I have a function that drop the tables of my plugin on DB.

?php

if (! defined('WP_UNINSTALL_PLUGIN')) {
exit;
}

// Uninstallation actions here

global $wpdb;

$table_names = [
    $wpdb-prefix . "questions",
    $wpdb-prefix . "difficulties",
    $wpdb-prefix . "modalities",
    $wpdb-prefix . "fields",
    $wpdb-prefix . "themes",
    $wpdb-prefix . "subjects",
    $wpdb-prefix . "disciplines",
    $wpdb-prefix . "training_areas",
    $wpdb-prefix . "levels",
    $wpdb-prefix . "roles",
    $wpdb-prefix . "banks",
];

foreach ($table_names as $table_name) {
    $wpdb-query("DROP TABLE IF EXISTS $table_name");
}

But when I delete the plugin on admin, it shows this error:

It does drop all the tables, but how I make to stop this error?