fix fields that shouldn't be required

MediaBrowser.XbmcMetadata/Savers/EpisodeNfoSaver.cs

@@ -64,25 +64,25 @@ namespace MediaBrowser.XbmcMetadata.Savers
                 writer.WriteElementString("aired", episode.PremiereDate.Value.ToLocalTime().ToString(formatString));
             }
 
-            if (episode.AirsAfterSeasonNumber.HasValue)
+            if (episode.AirsAfterSeasonNumber.HasValue && episode.AirsAfterSeasonNumber.Value != -1)
             {
                 writer.WriteElementString("airsafter_season", episode.AirsAfterSeasonNumber.Value.ToString(UsCulture));
             }
-            if (episode.AirsBeforeEpisodeNumber.HasValue)
+            if (episode.AirsBeforeEpisodeNumber.HasValue && episode.AirsBeforeEpisodeNumber.Value != -1)
             {
                 writer.WriteElementString("airsbefore_episode", episode.AirsBeforeEpisodeNumber.Value.ToString(UsCulture));
             }
-            if (episode.AirsBeforeEpisodeNumber.HasValue)
+            if (episode.AirsBeforeEpisodeNumber.HasValue && episode.AirsBeforeEpisodeNumber.Value != -1)
             {
                 writer.WriteElementString("displayepisode", episode.AirsBeforeEpisodeNumber.Value.ToString(UsCulture));
             }
-            if (episode.AirsBeforeSeasonNumber.HasValue)
+            if (episode.AirsBeforeSeasonNumber.HasValue && episode.AirsBeforeSeasonNumber.Value != -1)
             {
                 writer.WriteElementString("airsbefore_season", episode.AirsBeforeSeasonNumber.Value.ToString(UsCulture));
             }
 
             var season = episode.AiredSeasonNumber;
-            if (season.HasValue)
+            if (season.HasValue && season.Value != -1)
             {
                 writer.WriteElementString("displayseason", season.Value.ToString(UsCulture));
             }