Fix error with null dates

src/NzbDrone.Core/MetadataSource/SkyHook/SkyHookProxy.cs

@@ -142,18 +142,18 @@ namespace NzbDrone.Core.MetadataSource.SkyHook
             if (resource.release_date.IsNotNullOrWhiteSpace())
             {
                 movie.InCinemas = DateTime.Parse(resource.release_date);
-            }
 
-            // get the lowest year in all release date
-            var lowestYear = new List<int>();
-            foreach (ReleaseDates releaseDates in resource.release_dates.results)
-            {
-                foreach (ReleaseDate releaseDate in releaseDates.release_dates)
+                // get the lowest year in all release date
+                var lowestYear = new List<int>();
+                foreach (ReleaseDates releaseDates in resource.release_dates.results)
                 {
-                    lowestYear.Add(DateTime.Parse(releaseDate.release_date).Year);
+                    foreach (ReleaseDate releaseDate in releaseDates.release_dates)
+                    {
+                        lowestYear.Add(DateTime.Parse(releaseDate.release_date).Year);
+                    }
                 }
+                movie.Year = lowestYear.Min();
             }
-            movie.Year = lowestYear.Min();
 
             movie.TitleSlug += "-" + movie.TmdbId.ToString();