store: Show error message when replacing event queue.

Signed-off-by: Zixuan James Li <[email protected]>

Author: PIG208

lib/model/store.dart

@@ -782,6 +782,7 @@ class UpdateMachine {
           case ZulipApiException(code: 'BAD_EVENT_QUEUE_ID'):
             assert(debugLog('Lost event queue for $store.  Replacing…'));
             await store._globalStore._reloadPerAccount(store.accountId);
+            reportErrorToUserBriefly('Reconnecting to server.');
             dispose();
             debugLog('… Event queue replaced.');
             return;