Call envadjust() before updating VM stack.

src/vm.c

@@ -164,10 +164,10 @@ stack_extend_alloc(mrb_state *mrb, int room)
     mrb_exc_raise(mrb, mrb_obj_value(mrb->stack_err));
   }
   stack_clear(&(newstack[oldsize]), size - oldsize);
+  envadjust(mrb, oldbase, newstack);
   mrb->c->stbase = newstack;
   mrb->c->stack = mrb->c->stbase + off;
   mrb->c->stend = mrb->c->stbase + size;
-  envadjust(mrb, oldbase, mrb->c->stbase);
 
   /* Raise an exception if the new stack size will be too large,
      to prevent infinite recursion. However, do this only after resizing the stack, so mrb_raise has stack space to work with. */