Merge pull request #4220 from Spacetech/TvdbEpisodeImageProvider_nullable_check

Fix invalid operation exception in TvdbEpisodeImageProvider.GetImages

MediaBrowser.Providers/Plugins/TheTvdb/TvdbEpisodeImageProvider.cs

@@ -56,6 +56,10 @@ namespace MediaBrowser.Providers.Plugins.TheTvdb
             {
                 // Process images
                 try
+                {
+                    string episodeTvdbId = null;
+
+                    if (episode.IndexNumber.HasValue && episode.ParentIndexNumber.HasValue)
                     {
                         var episodeInfo = new EpisodeInfo
                         {
@@ -64,14 +68,17 @@ namespace MediaBrowser.Providers.Plugins.TheTvdb
                             SeriesProviderIds = series.ProviderIds,
                             SeriesDisplayOrder = series.DisplayOrder
                         };
-                    string episodeTvdbId = await _tvdbClientManager
+
+                        episodeTvdbId = await _tvdbClientManager
                             .GetEpisodeTvdbId(episodeInfo, language, cancellationToken).ConfigureAwait(false);
+                    }
+
                     if (string.IsNullOrEmpty(episodeTvdbId))
                     {
                         _logger.LogError(
                             "Episode {SeasonNumber}x{EpisodeNumber} not found for series {SeriesTvdbId}",
-                            episodeInfo.ParentIndexNumber,
+                            episode.ParentIndexNumber,
-                            episodeInfo.IndexNumber,
+                            episode.IndexNumber,
                             series.GetProviderId(MetadataProvider.Tvdb));
                         return imageResult;
                     }