check command dir exists

Author: walkor

src/webman

@@ -8,5 +8,7 @@ require_once __DIR__ . '/support/bootstrap.php';
 $cli = new Command();
 $cli->setName('webman cli');
 $cli->installInternalCommands();
-$cli->installCommands(app_path(). '/command');
+if (is_dir($command_path = app_path(). '/command')) {
+    $cli->installCommands($command_path);
+}
 $cli->run();