ignore subtitles when they are unavailable (#1583)

CHANGELOG.md

@@ -58,6 +58,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
   - This bug caused the ErsatzTV logo to be used instead of channel logos in some cases 
 - Update drop down search results in main search bar when items are created/edited/removed 
 - Fix green line at bottom of video when NVIDIA accel is used with intermittent watermark
+- Fix error starting streaming session when subtitles are still being extracted for the current item
 
 ### Changed
 - Upgrade from .NET 7 to .NET 8

ErsatzTV.Core/FFmpeg/FFmpegLibraryProcessService.cs

@@ -228,7 +228,7 @@ public class FFmpegLibraryProcessService : IFFmpegProcessService
         Option<SubtitleInputFile> subtitleInputFile = maybeSubtitle.Map<Option<SubtitleInputFile>>(
             subtitle =>
             {
-                if (!subtitle.IsImage && subtitle.SubtitleKind == SubtitleKind.Embedded && !subtitle.IsExtracted)
+                if (!subtitle.IsImage && subtitle.SubtitleKind == SubtitleKind.Embedded && (!subtitle.IsExtracted || string.IsNullOrWhiteSpace(subtitle.Path)))
                 {
                     _logger.LogWarning("Subtitles are not yet available for this item");
                     return None;