fix: prevent embed flash of "Failed to load dashboard" due to race in time range query (#9132)

Author: ericpgreen2

web-common/src/features/dashboards/state-managers/loaders/DashboardStateDataLoader.ts

@@ -251,8 +251,10 @@ export class DashboardStateDataLoader {
         }
 
         if (
-          fullTimeRange.data?.timeRangeSummary?.min == null &&
-          fullTimeRange.data?.timeRangeSummary?.max == null
+          !fullTimeRange.isLoading &&
+          fullTimeRange.data &&
+          fullTimeRange.data.timeRangeSummary?.min == null &&
+          fullTimeRange.data.timeRangeSummary?.max == null
         ) {
           // The timeRangeSummary is null when there are 0 rows of data.
           // Notably, this happens when a security policy fully restricts a user from reading any data.