Fix `mosquitto_passwd -U`

ChangeLog.txt

@@ -2,6 +2,9 @@ Broker:
 - Fix websockets connections on Windows blocking subsequent connections.
   Closes #1934.
 
+Apps:
+- Fix `mosquitto_passwd -U`
+
 Build:
 - Fix cjson include paths.
 - Fix build using WITH_TLS=no when the openssl headers aren't available.

apps/mosquitto_passwd/mosquitto_passwd.c

@@ -273,7 +273,11 @@ int delete_pwuser(FILE *fptr, FILE *ftmp, const char *username)
  * ====================================================================== */
 static int update_file_cb(FILE *fptr, FILE *ftmp, const char *username, const char *password, const char *line, struct cb_helper *helper)
 {
-	return output_new_password(ftmp, username, password, helper->iterations);
+	if(helper){
+		return output_new_password(ftmp, username, password, helper->iterations);
+	}else{
+		return output_new_password(ftmp, username, password, PW_DEFAULT_ITERATIONS);
+	}
 }
 
 int update_file(FILE *fptr, FILE *ftmp)