[PATCH] http-push: workaround for format overflow warning in gcc >= 9

[Carlo Marcelo Arenas Belón <carenas@xxxxxxxxx>]

In function 'finish_request',
    inlined from 'process_response' at http-push.c:248:2:
http-push.c:587:4: warning: '%s' directive argument is null [-Wformat-overflow=]
  587 |    fprintf(stderr, "Unable to get pack file %s\n%s",
      |    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  588 |     request->url, curl_errorstr);
      |     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
---
 http-push.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/http-push.c b/http-push.c
index f675a96316..2db553ef38 100644
--- a/http-push.c
+++ b/http-push.c
@@ -585,7 +585,8 @@ static void finish_request(struct transfer_request *request)
 		int fail = 1;
 		if (request->curl_result != CURLE_OK) {
 			fprintf(stderr, "Unable to get pack file %s\n%s",
-				request->url, curl_errorstr);
+				request->url ? request->url : "",
+				curl_errorstr);
 		} else {
 			preq = (struct http_pack_request *)request->userData;
 
-- 
2.21.0