Do not download files if find_dl_candidates() fails

One reason why the function returns an error is some repo
does not have any servers.
Signed-off-by: Anatol Pomozov <anatol.pomozov@gmail.com>
Signed-off-by: Allan McRae <allan@archlinux.org>

lib/libalpm/sync.c

@@ -787,7 +787,7 @@ static int download_files(alpm_handle_t *handle)
 
 	errors += find_dl_candidates(handle, &files);
 
-	if(files) {
+	if(files && !errors) {
 		/* check for necessary disk space for download */
 		if(handle->checkspace) {
 			off_t *file_sizes;