无法在Java脚本中读取null的属性样式

Question

如果值等于EM的字段颜色我尝试更改。以下是逻辑，它给出错误为Cannot read property 'style' of null。自工作类型== EM以来，if似乎进入if条件之内，但在下一行代码中给出错误。

define("custom/handlers/customBGColorHandler", ["dojo/_base/declare",
  "application/handlers/BGColorHandler",
  "dojo/_base/array",
  "dojo/_base/lang",
  "dojo/on",
  "dojo/dom-construct",
  "dojo/dom-attr",
  "dojo/dom-class",
  "dojo/dom",
  "dojo/dom-style",
  ...
  ...
]);


function(declare, array, lang, on, domConstruct, domAttr, dom, domStyle..) {
  return (BGColorHandler) {
    changeBackgroundColor: function(eventContext) {
      var currentWO = CommonHandler._getAdditionalResource(eventContext, 'workOrder').getCurrentRecord();
      var worktype = currentWO.get("worktype");
      if (worktype != null) {
        if (worktype == 'EM') {
          domStyle.set(worktype, "borderBottom", "10px solid red");
          domStyle.set(worktype, "background-color", "rgba(240,147,153,0.5)");

        } else {

          domStyle.set(worktype, "borderBottom", "");
          domStyle.set(worktype, "background-color", "");
        }
      }
    }
  });
}