Fix no-dupe-else-if issues (#9208)

See [`no-dupe-else-if`](https://eslint.org/docs/rules/no-dupe-else-if) for more information.

This change enables `no-dupe-else-if` and fixes the issues raised by the rule.

.eslintrc.js

@@ -49,6 +49,7 @@ module.exports = {
     'guard-for-in': 'error',
     'implicit-arrow-linebreak': 'error',
     'no-case-declarations': 'error',
+    'no-dupe-else-if': 'error',
     'no-empty': 'error',
     'no-eq-null': 'error',
     'no-global-assign': 'error',

ui/app/components/app/menu-droppo.js

@@ -37,8 +37,6 @@ export default class MenuDroppoComponent extends Component {
 
     if (isOpen) {
       this.outsideClickHandler = onClickOutside
-    } else if (isOpen) {
-      this.outsideClickHandler = null
     }
   }