Reoprt non-transient polling errors.

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

Author: PIG208

lib/model/store.dart

@@ -779,6 +779,7 @@ class UpdateMachine {
         switch (e) {
           case ZulipApiException(code: 'BAD_EVENT_QUEUE_ID'):
             assert(debugLog('Lost event queue for $store.  Replacing…'));
+            reportErrorToUserBriefly('Reconnecting to server.');
             await store._globalStore._reloadPerAccount(store.accountId);
             dispose();
             debugLog('… Event queue replaced.');
@@ -796,7 +797,7 @@ class UpdateMachine {
           default:
             assert(debugLog('Error polling event queue for $store: $e\n'
                 'Backing off and retrying even though may be hopeless…'));
-            // TODO tell user on non-transient error in polling
+            reportErrorToUserBriefly('Error loading server data, will retry: $e');
             await backoffMachine.wait();
             assert(debugLog('… Backoff wait complete, retrying poll.'));
             continue;