support trailers for episodes

MediaBrowser.Server.Implementations/Library/LibraryManager.cs

@@ -2309,7 +2309,7 @@ namespace MediaBrowser.Server.Implementations.Library
 
         public IEnumerable<Video> FindTrailers(BaseItem owner, List<FileSystemMetadata> fileSystemChildren, IDirectoryService directoryService)
         {
-            var files = fileSystemChildren.Where(i => i.IsDirectory)
+            var files = owner.IsInMixedFolder ? new List<FileSystemMetadata>() : fileSystemChildren.Where(i => i.IsDirectory)
                 .Where(i => string.Equals(i.Name, BaseItem.TrailerFolderName, StringComparison.OrdinalIgnoreCase))
                 .SelectMany(i => _fileSystem.GetFiles(i.FullName, false))
                 .ToList();