add write barrier to env on pop call info poped. #2525

src/vm.c

@@ -253,6 +253,7 @@ cipop(mrb_state *mrb)
       stack_copy(p, e->stack, len);
     }
     e->stack = p;
+    mrb_write_barrier(mrb, (struct RBasic *)e);
   }
 
   c->ci--;