fix adding alternate schedule (#1418)

CHANGELOG.md

@@ -25,6 +25,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 - Fix log viewer crash when log file contains invalid data
 - Clean channel guide cache on startup (delete channels that no longer exist)
 - Fix Emby movie libraries so local file access is not required
+- Fix adding alternate schedule
 
 ### Changed
 - Optimize transcoding session to only work ahead (at max speed) for 2 minutes before throttling to realtime

ErsatzTV.Application/Playouts/Commands/ReplacePlayoutAlternateScheduleItemsHandler.cs

@@ -119,6 +119,13 @@ public class ReplacePlayoutAlternateScheduleItemsHandler :
 
                 await dbContext.SaveChangesAsync(cancellationToken);
 
+                // load newly-added schedules
+                foreach (ProgramScheduleAlternate alternate in playout.ProgramScheduleAlternates
+                             .Where(alternate => alternate.ProgramSchedule is null))
+                {
+                    await dbContext.Entry(alternate).Reference(a => a.ProgramSchedule).LoadAsync(cancellationToken);
+                }
+
                 foreach (PlayoutItem _ in maybeLastPlayoutItem)
                 {
                     foreach (DateTimeOffset dayToCheck in daysToCheck)