store [nfc]: On loading account, notify global listeners

This makes GlobalStore behave a bit more conventionally for
a ChangeNotifier.

Author: gnprice

lib/model/store.dart

@@ -98,6 +98,7 @@ abstract class GlobalStore extends ChangeNotifier {
     store = await future;
     _perAccountStores[accountId] = store;
     _perAccountStoresLoading.remove(accountId);
+    notifyListeners();
     return store;
   }
 

lib/widgets/store.dart

@@ -192,10 +192,8 @@ class _PerAccountStoreWidgetState extends State<PerAccountStoreWidget> {
     if (store != null) {
       _setStore(store);
     } else {
-      // If we don't already have data, wait for it.
-      (() async {
-        _setStore(await globalStore.perAccount(widget.accountId));
-      })();
+      // If we don't already have data, request it.
+      globalStore.perAccount(widget.accountId);
     }
   }