apis / clusters-menu refactoring

Signed-off-by: Roman <ixrock@gmail.com>

src/common/cluster-store.ts

@@ -52,7 +52,7 @@ export class ClusterStore extends BaseStore<ClusterStoreModel> {
   @observable removedClusters = observable.map<ClusterId, Cluster>();
   @observable clusters = observable.map<ClusterId, Cluster>();
 
-  @computed get activeCluster(): Cluster {
+  @computed get activeCluster(): Cluster | null {
     return this.getById(this.activeClusterId);
   }