我正在嘗試使用d3plus.js將圖表添加到我的網站。我收到以下錯誤消息：Uncaught TypeError: Cannot read property 'buttons' of null    at SVGGElement.<anonymous> (d3plus.js:23745)    at SVGGElement.__onmousemove (d3.js:1120)我嘗試將腳本放置在頁面的開頭和頁腳之后。**head.php**    <script src="../wp-content/themes/sage/bower_components/d3/d3.js"> </script>    <script src="../wp-content/themes/sage/bower_components/d3plus/d3plus.js"></script>**page.php**    <div id="viz" width="1356" height="579"></div>    <script>    var data = [      {"year": 1991, "name":"alpha", "value": 15},      {"year": 1991, "name":"beta", "value": 10},      {"year": 1991, "name":"gamma", "value": 5},      {"year": 1991, "name":"delta", "value": 50},      {"year": 1992, "name":"alpha", "value": 20},      {"year": 1992, "name":"beta", "value": 10},      {"year": 1992, "name":"gamma", "value": 10},      {"year": 1992, "name":"delta", "value": 43},      {"year": 1993, "name":"alpha", "value": 30},      {"year": 1993, "name":"beta", "value": 40},      {"year": 1993, "name":"gamma", "value": 20},      {"year": 1993, "name":"delta", "value": 17},      {"year": 1994, "name":"alpha", "value": 60},      {"year": 1994, "name":"beta", "value": 60},      {"year": 1994, "name":"gamma", "value": 25},      {"year": 1994, "name":"delta", "value": 32}    ]    var visualization = d3plus.viz()      .container("#viz")      .data(data)      .type("bar")      .id("name")      .height(300)      .width(1100)      .x("year")      .y("value")      .draw()    </script>鼠標懸停時，標簽應顯示在圖表上，但出現錯誤消息：Uncaught TypeError: Cannot read property 'buttons' of null    at SVGGElement.<anonymous> (d3plus.js:23745)    at SVGGElement.__onmousemove (d3.js:1120)