fix sorting episodes without metadata (#353)

CHANGELOG.md

@@ -9,6 +9,8 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
   - Properly order elements
   - Omit channels with no programmes
   - Properly identify channels using the format number.etv like `15.etv`
+- Fix sorting episodes without episode metadata
+  - This bug prevented playouts from building and was most often seen when grouping multi-part episodes, as shows are sorted chronologically before checking for multi-part episodes
 
 ## [0.0.55-alpha] - 2021-09-03
 ### Fixed

ErsatzTV.Core/Scheduling/ChronologicalMediaComparer.cs

@@ -66,13 +66,17 @@ namespace ErsatzTV.Core.Scheduling
 
             int episode1 = x switch
             {
-                Episode e => e.EpisodeMetadata.Max(em => em.EpisodeNumber),
+                Episode e => e.EpisodeMetadata.HeadOrNone().Match(
+                    em => em.EpisodeNumber,
+                    () => int.MaxValue),
                 _ => int.MaxValue
             };
 
             int episode2 = y switch
             {
-                Episode e => e.EpisodeMetadata.Max(em => em.EpisodeNumber),
+                Episode e => e.EpisodeMetadata.HeadOrNone().Match(
+                    em => em.EpisodeNumber,
+                    () => int.MaxValue),
                 _ => int.MaxValue
             };