revert: Use empty() for environment variable checks in example

Author: OskarStark

examples/albert/chat.php

@@ -10,12 +10,12 @@
 
 require_once dirname(__DIR__).'/../vendor/autoload.php';
 
-if (!isset($_ENV['ALBERT_API_KEY'])) {
+if (empty($_ENV['ALBERT_API_KEY'])) {
     echo 'Please set the ALBERT_API_KEY environment variable.'.\PHP_EOL;
     exit(1);
 }
 
-if (!isset($_ENV['ALBERT_API_URL'])) {
+if (empty($_ENV['ALBERT_API_URL'])) {
     echo 'Please set the ALBERT_API_URL environment variable (e.g., https://your-albert-instance.com).'.\PHP_EOL;
     exit(1);
 }