Improve add/loading error notices

(cherry picked from commit dd704579df43b0dd835f8bb618c4b4412561a888)

Closes #9767

frontend/src/Settings/Indexers/Indexers/EditIndexerModalContent.js

@@ -1,5 +1,6 @@
 import PropTypes from 'prop-types';
 import React from 'react';
+import Alert from 'Components/Alert';
 import Form from 'Components/Form/Form';
 import FormGroup from 'Components/Form/FormGroup';
 import FormInputGroup from 'Components/Form/FormInputGroup';
@@ -66,9 +67,9 @@ function EditIndexerModalContent(props) {
 
         {
           !isFetching && !!error &&
-            <div>
+            <Alert kind={kinds.DANGER}>
               {translate('AddIndexerError')}
-            </div>
+            </Alert>
         }
 
         {

frontend/src/Settings/Indexers/Indexers/Indexer.js

@@ -42,7 +42,7 @@ class Indexer extends Component {
     });
   };
 
-  onDeleteIndexerModalClose= () => {
+  onDeleteIndexerModalClose = () => {
     this.setState({ isDeleteIndexerModalOpen: false });
   };