fix z-index sorting in graphics engine (#2786)

CHANGELOG.md

@@ -25,7 +25,9 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 
 ### Fixed
 - Use code signing on all Windows executables (`ErsatzTV-Windows.exe`, `ErsatzTV.exe`, `ErsatzTV.Scanner.exe`)
-- Respect `z_index` (draw order) on all graphics element types
+- Graphics engine:
+  - Respect `z_index` (draw order) on all graphics element types
+  - Fix bug with `z_index` sorting
 - Restore default UI font that was erroneously removed in v26.1.1
 - Use configured searching log level on startup, instead of the default log level of `Information`
 - MySql: fix searching for shows and seasons in schedule items editor

ErsatzTV.Infrastructure/Streaming/Graphics/GraphicsEngine.cs

@@ -156,7 +156,7 @@ public class GraphicsEngine(
                     }
                 }
 
-                preparedElementImages.Sort((a, _) => a.ZIndex);
+                preparedElementImages.Sort((a, b) => a.ZIndex.CompareTo(b.ZIndex));
 
                 Memory<byte> memory = pipeWriter.GetMemory(frameBufferSize);