[Bug]: 分组柱图，如果某个值为null，在tooltips为shared情况下，没有该值的提示 #6754

Describe the bug / 问题描述

测试代码

import { Chart } from "@antv/g2";

const chart = new Chart({ container: "container" });

chart.options({
  type: "interval",
  autoFit: true,
  data: [
    { name: "London", 月份: "Jan.", 月均降雨量: 18.9 },
    { name: "London", 月份: "Feb.", 月均降雨量: 28.8 },
    { name: "London", 月份: "Mar.", 月均降雨量: 39.3 },
    { name: "London", 月份: "Apr.", 月均降雨量: null },
    { name: "London", 月份: "May", 月均降雨量: 47 },
    { name: "London", 月份: "Jun.", 月均降雨量: 20.3 },
    { name: "London", 月份: "Jul.", 月均降雨量: 24 },
    { name: "London", 月份: "Aug.", 月均降雨量: 35.6 },
    { name: "Berlin", 月份: "Jan.", 月均降雨量: 12.4 },
    { name: "Berlin", 月份: "Feb.", 月均降雨量: 23.2 },
    { name: "Berlin", 月份: "Mar.", 月均降雨量: 34.5 },
    { name: "Berlin", 月份: "Apr.", 月均降雨量: 99.7 },
    { name: "Berlin", 月份: "May", 月均降雨量: 52.6 },
    { name: "Berlin", 月份: "Jun.", 月均降雨量: 35.5 },
    { name: "Berlin", 月份: "Jul.", 月均降雨量: 37.4 },
    { name: "Berlin", 月份: "Aug.", 月均降雨量: null },
  ],
  encode: { x: "月份", y: "月均降雨量", color: "name" },
  transform: [{ type: "dodgeX" }],
  interaction: {
    tooltip: {
      shared: true
    }, elementHighlight: { background: true }
  },
});

chart.render();

实际

期望

Reproduction link / 复现链接

No response

Steps to Reproduce the Bug or Issue / 重现步骤

No response

Version / 版本

🆕 5.x

OS / 操作系统

• macOS
• Windows
• Linux
• Others / 其他

Browser / 浏览器

• Chrome
• Edge
• Firefox
• Safari (Limited support / 有限支持)
• IE (Nonsupport / 不支持)
• Others / 其他