Add `directLinkedGroupFetchFailed` selector

Avoid accessing state via `getState()`

src/sidebar/store/modules/direct-linked.js

@@ -136,6 +136,10 @@ function directLinkedGroupId(state) {
   return state.directLinked.directLinkedGroupId;
 }
 
+function directLinkedGroupFetchFailed(state) {
+  return state.directLinked.directLinkedGroupFetchFailed;
+}
+
 export default {
   init,
   namespace: 'directLinked',
@@ -149,6 +153,7 @@ export default {
   },
   selectors: {
     directLinkedAnnotationId,
+    directLinkedGroupFetchFailed,
     directLinkedGroupId,
   },
 };

src/sidebar/store/modules/test/direct-linked-test.js

@@ -88,6 +88,13 @@ describe('sidebar/store/modules/direct-linked', () => {
       });
     });
 
+    describe('#directLinkedGroupFetchFailed', () => {
+      it('should return the group fetch failed status', () => {
+        store.setDirectLinkedGroupFetchFailed(true);
+        assert.isTrue(store.directLinkedGroupFetchFailed());
+      });
+    });
+
     describe('#directLinkedGroupId', () => {
       it('should return the current direct-linked group ID', () => {
         store.setDirectLinkedGroupId('group-id');