Update MediaBrowser.Providers/Plugins/Tmdb/TV/TmdbEpisodeImageProvider.cs

Co-authored-by: Cody Robibero <cody@robibe.ro>

MediaBrowser.Providers/Plugins/Tmdb/TV/TmdbEpisodeImageProvider.cs

@@ -61,7 +61,7 @@ namespace MediaBrowser.Providers.Plugins.Tmdb.TV
 
             var seriesTmdbId = Convert.ToInt32(series?.GetProviderId(MetadataProvider.Tmdb), CultureInfo.InvariantCulture);
 
-            if (series == null || seriesTmdbId <= 0)
+            if (series is null || seriesTmdbId <= 0)
             {
                 return Enumerable.Empty<RemoteImageInfo>();
             }