Unexpected result when modifying a table (wrong safeenv/optimization)

[khvzak]

Initially discovered in mlua-rs/mlua#485

Easy to reproduce using Luau cli:

$ luau
> state = {i = 0}
> print("before:", state.i); state.i = state.i + 1; print("after: ", state.i);
before:	0
after: 	0

Setting optimization level to 0 OR removing lua_setsafeenv call will give right result:

❯ luau -O0
> state = {i = 0}
> print("before:", state.i); state.i = state.i + 1; print("after: ", state.i);
before:	0
after: 	1

Luau v0.652