fetchActions: Also abort on app-internal errors in the initial fetch.

As Greg points out [1]:

> Basically it's an internal error in the app. But the user is
> probably better off getting kicked back to the account picker than
> having the loading screen continue indefinitely -- it means at
> least they can try again and see if the issue recurs, or try
> another account and see if they can at least use that.

[1] zulip#4754 (comment)

src/message/fetchActions.js

@@ -413,6 +413,7 @@ export const doInitialFetch = () => async (dispatch: Dispatch, getState: GetStat
     } else if (e instanceof TimeoutError) {
       dispatch(initialFetchAbort('timeout'));
     } else {
+      dispatch(initialFetchAbort('unexpected'));
       logging.warn(e, {
         message: 'Unexpected error during initial fetch and serverSettings fetch.',
       });