[explore-v2] Fix edit datasource link for druid datasources (#1982)

* only add imgSrc key if choices contain an imgSrc

* handle table and druid edit links for datasource drop down

* fix linting

superset/assets/javascripts/explorev2/components/SelectField.jsx

@@ -43,15 +43,13 @@ export default class SelectField extends React.Component {
   }
   getOptions() {
     const options = this.props.choices.map((c) => {
-      let label = c[0];
-      if (c.length > 1) {
-        label = c[1];
-      }
-      return {
+      const label = c.length > 1 ? c[1] : c[0];
+      const newOptions = {
         value: c[0],
         label,
-        imgSrc: c[2],
       };
+      if (c[2]) newOptions.imgSrc = c[2];
+      return newOptions;
     });
     if (this.props.freeForm) {
       // For FreeFormSelect, insert value into options if not exist