Update src/client/sse.ts

nullish coalescing operator ?? instead of the logical OR operator || to handle the case where this?._eventSourceInit?.fetch or this._fetch might be null or undefined but not falsy

Co-authored-by: gemini-code-assist[bot] <176961590+gemini-code-assist[bot]@users.noreply.github.com>

Author: cliffhall

src/client/sse.ts

@@ -126,7 +126,7 @@ export class SSEClientTransport implements Transport {
   }
 
   private _startOrAuth(): Promise<void> {
-    const fetchImpl = (this?._eventSourceInit?.fetch || this._fetch || fetch) as typeof fetch
+const fetchImpl = (this?._eventSourceInit?.fetch ?? this._fetch ?? fetch) as typeof fetch
     return new Promise((resolve, reject) => {
       this._eventSource = new EventSource(
         this._url.href,