Address review comment

src/gui/guiEngine.cpp

@@ -663,14 +663,15 @@ bool GUIEngine::downloadFile(const std::string &url, const std::string &target)
 	fetch_request.caller = HTTPFETCH_SYNC;
 	fetch_request.timeout = std::max(MIN_HTTPFETCH_TIMEOUT,
 		(long)g_settings->getS32("curl_file_download_timeout"));
-	if (!httpfetch_sync_interruptible(fetch_request, fetch_result))
-		return false;
+	bool completed = httpfetch_sync_interruptible(fetch_request, fetch_result);
 
-	if (!fetch_result.succeeded) {
+	if (!completed || !fetch_result.succeeded) {
 		target_file.close();
 		fs::DeleteSingleFileOrEmptyDirectory(target);
 		return false;
 	}
+	// TODO: directly stream the response data into the file instead of first
+	// storing the complete response in memory
 	target_file << fetch_result.data;
 
 	return true;