Avoid exec the getAvailability function when there are`t calendar selected (#9192)

Co-authored-by: Joe Au-Yeung <65426560+joeauyeung@users.noreply.github.com>
Co-authored-by: Hariom Balhara <hariombalhara@gmail.com>

packages/core/CalendarManager.ts

@@ -151,6 +151,7 @@ export const getCachedResults = async (
      * TODO: Migrate credential type or appId
      */
     const passedSelectedCalendars = selectedCalendars.filter((sc) => sc.integration === type);
+    if (!passedSelectedCalendars.length) return [];
     /** We extract external Ids so we don't cache too much */
     const selectedCalendarIds = passedSelectedCalendars.map((sc) => sc.externalId);
     /** If we don't then we actually fetch external calendars (which can be very slow) */