Fixed bugs found by psalm

Author: Nyholm

Command/ServerDumpCommand.php

@@ -95,5 +95,7 @@ protected function execute(InputInterface $input, OutputInterface $output): int
         $this->server->listen(function (Data $data, array $context, int $clientId) use ($descriptor, $io) {
             $descriptor->describe($io, $data, $context, $clientId);
         });
+
+        return 0;
     }
 }