json-file: avoid allocation

src/output-json-file.c

@@ -128,14 +128,11 @@ static void FileWriteJsonRecord(JsonFileLogThread *aft, const Packet *p, const F
             if (ff->flags & FILE_MD5) {
                 size_t x;
                 int i;
-                char *s = SCMalloc(256);
-                if (likely(s != NULL)) {
+                char s[256];
                 for (i = 0, x = 0; x < sizeof(ff->md5); x++) {
                     i += snprintf(&s[i], 255-i, "%02x", ff->md5[x]);
                 }
                 json_object_set_new(fjs, "md5", json_string(s));
-                    SCFree(s);
-                }
             }
 #endif
             break;