BHttpRequest: Fix the cast and therefor GCC2 build

Change-Id: Ia0729a20d143721d395d5d50719e87b99b76bb05
Reviewed-on: https://review.haiku-os.org/c/haiku/+/3614
Reviewed-by: Stephan Aßmus <superstippi@gmx.de>

src/kits/network/libnetapi/HttpRequest.cpp

@@ -1212,5 +1212,5 @@ BHttpRequest::_NotifyDataReceived(const char* data, off_t pos, ssize_t size,
 	}
 	fListener->DataReceived(this, data, pos, size);
 	fListener->DownloadProgress(this, bytesReceived,
-		std::max((off_t)0, bytesTotal));
+		std::max((ssize_t)0, bytesTotal));
 }