Fix use-after-free in fuzzpuzz

When reporting that the game name in a save file isn't recognised,
don't include the name from the save file in the error message, partly
to avoid the complexity of freeing it properly on two different code
paths and partly because including unsanitized data from a
fuzzer-supplied save file in the error message just seems dangerous.
And properly sanitising it would waste the fuzzer's time exploring the
sanitising code.

Thanks to Ben Hutchings for reporting the bug.

fuzzpuzz.c

@@ -81,7 +81,7 @@ int main(int argc, char **argv)
                 ourgame = gamelist[i];
         sfree(gamename);
         if (ourgame == NULL) {
-            fprintf(stderr, "Game '%s' not recognised\n", gamename);
+            fprintf(stderr, "Game not recognised\n");
             ret = 1;
             continue;
         }