Pass globals on re-run

Without this, you end up with nasty race conditions when you're using globals and the sandcastle gets kicked over. E.g.:

1. Pass `while(true){}` to sandcastle
2. Before that script is finished, pass `exit(some_globals_variable)` to sandcastle
3. Sandcastle gets kicked over because the `while(true){}` timed out
4. The new sandcastle runs `exit(some_globals_variable)`, but now it has no `globals` so the script crashes