Avoid ubsan error in accessing action parameters (#1268)

Fixes #1230

Signed-off-by: Jiwon Kim <kjw6855@gmail.com>

src/bm_sim/actions.cpp

@@ -424,7 +424,7 @@ ActionFnEntry::execute(Packet *pkt) const {
  (primitive.get_source_info() == nullptr) ? "(no source info)"
  : primitive.get_source_info()->get_source_fragment());
  param_offset = primitive.get_param_offset();
- primitive.execute(&state, &(action_fn->params[param_offset]));
+ primitive.execute(&state, action_fn->params.data() + param_offset);
  idx = primitive.get_jump_offset(idx);
  }
 }