Message: Fix removed element offsetHeight calculation bug

[Aras-ax]

message组件，同时弹出多个消息的情况下，前一个消息框消失，计算offsetHeight的元素选择错误，会出现后面的消息框没置顶，或者覆盖的情况，在线演示见message bug

错误见代码中的注释

Message.close = function(id, userOnClose) {
  let len = instances.length;
  let index = -1;
  for (let i = 0; i < len; i++) {
    if (id === instances[i].id) {
      index = i;
      if (typeof userOnClose === 'function') {
        userOnClose(instances[i]);
      }
      instances.splice(i, 1);
      break;
    }
  }
  if (len <= 1 || index === -1 || index > instances.length - 1) return;
 // 这个地方计算的是 instances.splice(i, 1);移除后数组中的实例，index对应的instance不是被移除的那个元素，计算的offsetHeight 不正确
  const removedHeight = instances[index].$el.offsetHeight;
  for (let i = index; i < len - 1 ; i++) {
    let dom = instances[i].$el;
    dom.style['top'] =
      parseInt(dom.style['top'], 10) - removedHeight - 16 + 'px';
  }
};

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[island205]

Thanks
Duplicate of #17852