fix(operator): only show error empty state when no rundown data is available

The operator view previously replaced its content with the full-page
error state on any query error, even when a previously fetched rundown
was still cached. Now it falls back to rendering the cached data and
only shows the error placeholder if a rundown has never been received.

apps/client/src/features/operator/Operator.tsx

@@ -36,7 +36,8 @@ export default function OperatorLoader() {
     return <Loader />;
   }
 
-  if (status === 'error') {
+  // only show the error state if we have never received data to fall back on
+  if (status === 'error' && data.rundown.revision === -1) {
     return <EmptyPage variant='error' text='There was an error fetching data, please refresh the page.' />;
   }