https://github.com/curl/curl/commit/1c9cfb7af368feefb522caf81b052ee742a76da8
From: Daniel Stenberg <daniel@haxx.se>
Date: Mon, 20 Feb 2023 18:35:13 +0100
Subject: [PATCH] tool_operate: avoid fclose(NULL) on bad header dump file
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Fixes #10570
Reported-by: Jérémy Rabasco
Closes #10571
--- a/src/tool_operate.c
+++ b/src/tool_operate.c
@@ -984,12 +984,13 @@ static CURLcode single_transfer(struct GlobalConfig *global,
              */
             if(!per->prev || per->prev->config != config) {
               newfile = fopen(config->headerfile, "wb+");
-              fclose(newfile);
+              if(newfile)
+                fclose(newfile);
             }
             newfile = fopen(config->headerfile, "ab+");
 
             if(!newfile) {
-              warnf(global, "Failed to open %s\n", config->headerfile);
+              errorf(global, "Failed to open %s\n", config->headerfile);
               result = CURLE_WRITE_ERROR;
               break;
             }