Merge pull request #303 from ESP32Async/warning

Fix compiler warning

Author: mathieucarbou

src/WebHandlers.cpp

@@ -234,7 +234,11 @@ void AsyncStaticWebHandler::handleRequest(AsyncWebServerRequest *request) {
       size_t fileSize = request->_tempFile.size();
       etagValue = static_cast<uint32_t>(fileSize);
     }
+#ifndef ESP8266
+    snprintf(etag, sizeof(etag), "%08lx", etagValue);
+#else
     snprintf(etag, sizeof(etag), "%08x", etagValue);
+#endif
   } else {
     etag[0] = '\0';
   }