fix %d -> %u conversion

src/logging/wtts_log.c

@@ -149,7 +149,7 @@ void wtts_log(struct stardata_t * RESTRICT const stardata,
         if(fp==NULL)
         {
             char f[200];
-            int ret = snprintf(f,9,"./star%d",i);
+            int ret = snprintf(f,9,"./star%u",i);
             if(ret < 0){
                 /* enforce truncation */
                 f[199] = '\0';