Fix psalm issue and pin version

Author: trowski

composer.json

@@ -47,7 +47,7 @@
         "amphp/php-cs-fixer-config": "^2",
         "phpunit/phpunit": "^9",
         "psr/log": "^1",
-        "psalm/phar": "^5.18"
+        "psalm/phar": "~5.26.1"
     },
     "autoload": {
         "psr-4": {

src/Rfc6455Connector.php

@@ -111,13 +111,13 @@ private function generateRequest(WebsocketHandshake $handshake, string $key): Re
         $request->setTlsHandshakeTimeout($handshake->getTlsHandshakeTimeout());
         $request->setHeaderSizeLimit($handshake->getHeaderSizeLimit());
 
-        $extensions = Http\splitHeader($request, 'sec-websocket-extensions');
+        $extensions = Http\splitHeader($request, 'sec-websocket-extensions') ?? [];
 
         if ($this->compressionContextFactory && \extension_loaded('zlib')) {
             $extensions[] = $this->compressionContextFactory->createRequestHeader();
         }
 
-        if (!empty($extensions)) {
+        if ($extensions) {
             $request->setHeader('sec-websocket-extensions', \implode(', ', $extensions));
         }